A new survey of the upper chambers of Snefru's pyramids at Dahshur

Abstract

This article presents a new survey of the corbelled chambers within Snefru’s Bent and Red pyramids at Dahshur, based on photogrammetry work carried out by French company Iconem in 2018. As a consultant to the project, the author was involved in the research design and gave the company guidance on where to focus their efforts to optimize data acquisition and survey effectiveness. Once the data was processed, an analysis of the architecture was carried out and is reported here for the first time. The site survey history including pre-existing reports for the spaces of interest are first reviewed. The 3-dimensional digital models of the interior spaces are then analyzed. High-quality photogrammetry images from the project are presented here, along with new diagrams and a new description of the formation history of the funerary chambers.

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Cite this article:
F. Monnier, ‘A new survey of the upper chambers of Snefru’s pyramids at Dahshur’, JAEA 4,
2020, pp. 1-17.
The Journal of Ancient Egypan Architecture
vol. 4, 2020
www.egyptian-architecture.comJAEA
ISSN 2472-999X
Published under Creative Commons CC-BY-NC 2.0
A new survey of the upper chambers of
Snefru’s pyramids at Dahshur
Franck Monnier

Franck Monnier
Abstract:
This article presents a new survey of the corbelled chambers within Snefru’s Bent and Red pyramids
at Dahshur, based on photogrammetry work carried out by French company Iconem in 2018. As a
consultant to the project, the author was involved in the research design and gave the company guidance
on where to focus their efforts to optimize data acquisition and survey effectiveness. Once the data was
processed, an analysis of the architecture was carried out and is reported here for the rst time. The site
survey history including pre-existing reports for the spaces of interest are rst reviewed. The 3-dimensional
digital models of the interior spaces are then analyzed. High-quality photogrammetry images from the
project are presented here, along with new diagrams and a new description of the formation history of the
funerary chambers.
In the fall of 2018,1 a new photogrammetry survey was carried out in order to investigate the
potential of this imaging technique to enhance the study of pyramids. This work took place with the
permission of the Egyptian antiquities authorities and in coordination with a documentary series
produced by Label News.2 Over the course of the survey, the French start-up company Iconem
took thousands of digital photos with a drone in order to digitize the outer surfaces of the pyramid
of Djoser at Saqqara, the pyramids of Snefru at Meidum and Dahshur, the pyramids of Khufu,
Khafra, and Menkaure at Giza, and nally the pyramid of Redjedef at Abu Rawash. The internal
funerary chamber arrangements of some of these monuments were also scanned and have been
partially reconstructed in the form of 3D digital models. The method consisted of establishing
positions in three-dimensional space for every point visible on the surface of each monument. The
point locations were calculated by digitally processing a large number of overlapping photographs
which were taken from different angles. The result is a dense point-cloud that creates a 3D digital
model of the monument and incorporates the textured appearance of its surfaces, which can also
be deduced from the photographs.
As an expert consultant on the project, I was given access to the datasets acquired in order to
evaluate and analyse the data scientically. The results of those studies will be published in a series
of articles. This rst paper inaugurates the series with a reassessment of the upper chambers of the
Bent Pyramid at Dahshur-South and the Red Pyramid at Dahshur-North, based on the information
gathered in the new survey, and with reference to established studies of these monuments.
1 I’m very grateful to David Ian Lightbody for proof-reading the English text of the manuscript, and to Felix Arnold for his
constructive comments. Any remaining mistakes are the author’s responsability.
2 Pyramids: Solving the mysteries, produced by Label News and created by French director François Pomès whom I thank and
acknowledge for giving me the rights to analyze and to reproduce the data obtained during these documentaries.
JAEA 4, 2020, pp. 1-17.
A new survey of the upper chambers of Snefru’s
pyramids at Dahshur
www.egypan-architecture.com

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Fig. 1. Sectional and plan views of the inner arrangements of the Bent Pyramid drawn by John
Shae perring (Perring (1842), pl. XV).

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The upper chamber of the Bent Pyramid
Early descriptions
Modern exploration of the Bent Pyramid was started by John Shae Perring in 1839.3 He carried
out the difcult task of clearing the northern descending passage of stone rubble, which blocked
access to the chambers within. In the process, he was able to explore the entire system of spaces
and nally reached the upper chamber. He was the rst to produce section drawings (g. 1) and a
textual description of the space:
‘The eastern end of the horizontal passage communicated with an apartment 21 feet 6 inches long,
13 feet 6 inches wide, and 52 feet 6 inches high. It had been constructed like the other, and had been
built up to a great height with small stones. An excavation had been carried on, to the length of about
12 feet, into this masonry near the oor, and the apartment had been entirely ruined.’4
Exploration continued thereafter, but it was not until 1946, nearly a century later, that the rst
real scientic survey was organized. The work was led by the Egyptian Egyptologist Abd el-Salam
3 However, the English diplomat Davison entered into it in 1763 through the northern entrance and pushed along the
descending corridor. He could not go further; the corridor being completely blocked by a heap of rubble. Perring was the rst to
successfully access the more distant rooms during fall 1839, which enabled him to explore the entire building (Perring (1842),
p. 16). Regarding an unlikely earlier exploration of the pyramid by the travellers Melton and Lebrun, readers should refer to
Pickavance (1981).
4 Perring (1842), p. 17 ; Vyse (1840), p. 69.
Fig. 2. Two photos of the upper chamber of the Bent Pyramid (left: toward the South-West; right: toward
the North-West) taken by Abd el-Salam Hussein in the 1940s (Garnons Williams (1947), p. 305).

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Hussein,5 but he passed away suddenly in 1949 without having had the time to publish the results.6
An article in the British journal The Illustrated London News did, however, provide a brief account of
what Hussein was able to achieve.7 It contained some valuable photographs of the upper chamber
when it was still in its original state (g. 2), as well as a brief survey description:
‘The upper chamber when found was lled with hewn stone except for the southern side, which had a
passage about 3 ft. wide to a depth of 7 ft. Clearance of the upper part of this chamber revealed that
a box-shaped building had been inserted into it. The stone for this structure was smaller than that of
the chamber walls, but evidence suggested that a large portion of the masonry of this building was
contemporary with the pyramid itself, and that a staircase had originally led from oor-level up to the
roof of this building 23 ft. above the oor-level of the main room. Subsequent examination of the
roof of this structure has shown that certain paving-stones appear to have been inserted vertically,
since they are packed into position by small pieces of stone. Work at present in progress is therefore
directed at removing the pavement at this point in an endeavour to nd a lled shaft which should
lead surely to the burial chamber. (…) The walls of the upper chamber contain cracks which are lled
with ancient gypsum. This gypsum is thought to be contemporary with the building. It seems likely
that these cracks appeared during the construction of the pyramid, that they were observed and lled
with gypsum, and that in consequence the architect decided that the roof of the upper chamber
could not support the weight of the upper part of a true pyramid and so altered the outside angle,
which had the effect of lessening the eventual weight which the roof had to bear.’8
In the article, the author Captain P. A. J. Garnons Williams set out el-Salam Hussein’s plan to nd
a still intact burial chamber. He thought that the masonry mass lling the lower part of the upper
chamber was a sort of box in which the sarcophagus of Snefru was embedded.9 The masonry
mass was then dismantled in order to test the hypothesis. In the 1950s, Ahmed Fakhry continued
the exploration work started by el-Salam. He briey described the chamber and what he found in
these terms:
‘The upper chamber was also lled with comparatively small blocks of masonry more or less like those
which lled the lower chamber to the height of at least ve metres above the oor of the chamber. The
dimensions of this chamber are 6.70 ms. north-south and 5.20 ms. east-west and 16.50 ms. in height.
The blocks of its ceiling are badly damaged; a great part of it has fallen down and there is always a fear
that other parts might fall. However, during the last twelve years no fragments of it have fallen.
A part of the small stone blocks was removed from the chamber by robbers in ancient times in the
north eastern part of the chamber, and also in the south eastern corner which looks like a shaft.
The ancient treasure hunters tried also to make a tunnelling through this masonry; the cartouche of
Sneferu, which is the only occurrence of the name of this king inside the pyramid, is written on one
of the blocks which was exposed by the ancient treasure hunters. It is written in red ochre in the
quarry and is put upside down. The removal of the stone blocks was no doubt in search of the burial
place of Sneferu.
In the year 1946, Abdulsalam began to remove these small blocks in the hope of nding the burial
place of Sneferu underneath them. On dismantling the stones in the middle of the chamber, some
cedar beams were noticed lying among the masonry. When the stones were removed from most of
5 Abd el-Hassam Hussein is then assisted by Alexandre Varille (Varille (1947)).
6 Fakhry (1959), pp. 10-13.
7 Issue dated 22th march 1947 (Garnons Williams (1947)) and an unsigned article published the 8th April 1947.
8 Garnons Williams (1947), p. 303.
9 Ibidem.

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the chamber it was found that beams (halves of tree trunks) of cedar were put against the walls, four
of them against each of the eastern and western walls and three against the northern wall and other
beams were put on their tops. When all the stone blocks were removed, and the cedar beams stood
free their shape resembled a canopy not unlike that of Hetepheres in the general outlines. In the
middle of the oor there was found a key-stone which was also removed but no further dismantling
was done, as it looked rather hopeless to go down any further. During the four seasons which I spent
digging at Dahshur, my work inside the pyramid was limited to the opening of the western entrance
only; I did not try to dismantle more stones from any chamber although there were tempting reasons
to continue.’10
Ahmed Fakhry was assisted by the surveyor Hassan Mustapha who made precise measurements of
the whole pyramid.11 Although his published report contains a section drawing of the inside of the
monument, it seems that the Egyptian engineer reproduced some values which were already obtained
by Fakhry. After underlining the exceptional accuracy of the measurements made by Perring,12
Mustapha concluded by saying: ‘The interior of this pyramid has been examined but I can never
pretend that it has been thoroughly investigated or it does not need more researches in the future’.13
10 Fakhry (1959), p. 52.
11 Fakhry (1959), pp. 65-74.
12 In fact, Perring’s measurements and survey were not that precise. In the light of their judgment, I suspect that Fakhry and
Mustapha conned themselves to reproducing several of Perring’s measurements without verifying them. That would explain
why the upper chamber was so badly described for such a long time.
13 Fakhry (1959), p. 73.
Fig. 3. Section views of the upper chamber of the Bent Pyramid (left: toward the North; right:
toward the West) after Maragioglio and Rinaldi (Maragioglio and Rinaldi (1963), tav. 12).

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In the early 1960s, Italian architects Vito Maragioglio and Celeste Rinaldi compiled an architectural
report with an unprecedented level of attention to detail. Today, it remains an essential resource
for research scholars.14 The pair did not, however, have the material resources to undertake full
measurements of the interior spaces. They compiled their dataset by combining the new measures
with those from the earlier reports:
‘This chamber is 16.50 m. high (Hassan Mustafa) and 16 overhangs in the four walls form its corbelled
roof. The overhangs are very rough and hardly visible. (...)
At a certain height the southern face of the massif offsets for 27 cm. The passage between the
masonry massif and the south wall of the chamber was not empty, but lled up, to a certain extent,
with stone blocks. The inner blocks were squared and laid with mortar, the outer blocks were shapeless
and laid dry. This lling formed a kind of very steep ramp joining the entrance of the chamber with
the upper level of the masonry massif. (...)
Concerning the masonry massif, only a thickness of about 2.50 m remains at the south while it
appears from some photographs that originally it was practically untouched. During the dismantling
of this massif, the workers took away its [top surface layer] (P3) as well as a kind of oor (P2) laid
down in correspondence with the before mentioned offset. Proceeding in their excavation, they
reached the oor P1 of the chamber. From some photographs the oor P2 seems to have been built
with big limestone slabs and some of them were cut in order to t each other. The central slabs of
P2 were smaller than the peripheric ones, and some of them were really very small. In P1, [still] in the
central part, there was an L-shaped block that Fakhry calls a ‘Key-stone’. It was removed but nothing
was found underneath. Both oors (P1 and P2) were dressed but not smoothed.
Three holes, some containing beam stumps, were found in each of the east and west walls of the
chamber, between P3 and P2. Moreover, a framework of vertical and horizontal beams was found
between P2 and P1: the beams are cedar trunks just barked or only roughly hewn. There are three
vertical beams along the north wall, four along the east, and three along the west wall, but a fourth
one is certainly covered by the remaining masonry. Between the vertical beams placed along the east
and the west walls, horizontal beams were inserted at two different heights. The lower beams were
placed at about 2.90 m. The walls of the lower part of the chamber where they have been uncovered
by the ablation of the massif masonry are very rough, but we were not able to ascertain whether
such an aspect was due to rough work or caused by corrosion and stone aking. The same thing
also applies to the overhangs of the corbelled roof of the chamber. Even if they do not present any
cracks or yielding due to the superimposed weight, the horizontal edges, which are very sharp and
almost intact in the lower chamber, are here damaged to a great extent. In some parts it might even
seem that overhangs with sharp and precise corners were not foreseen.’15
To date, no other missions have been carried out to further enhance the corpus of information
about the chambers of this unusual site.16
In 2016, Alexander Puchkov and I used recent photographs of the chamber to reveal that it
underwent signicant changes during and after its construction, and that its current state was
the consequence of those modications.17 We were able to establish a chronological sequence of
events that explained the current state of the room and demonstrated this with the help of new
drawn sectional views. These were based on existing plans and reports, in particular those made by
14 Maragioglio and Rinaldi (1964), pp. 54-122, pls. 8-13.
15 Maragioglio and Rinaldi (1964), pp. 71-72.
16 An illustrated description of the interior has recently been published (Haase (2007)).
17 Monnier and Puchkov (2016), pp. 21-24.

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Maragioglio and Rinaldi, but were updated with regard to our new observations. We were, however,
missing a method to produce more accurate views, as we found that the existing surveys were not
clear with respect to some details and areas, and that further clarication was needed.18
In the same year, Gilles Dormion and Jean-Yves Verd’hurt published a book on the Bent Pyramid
in which they tried to demonstrate the existence of a secret chamber.19 We do not agree with
their analysis and conclusions,20 but their study contained interesting information, in particular a
reassessment of the height of the upper chamber which they claimed should be 13.90 m high and
not 16.50 m, as it was usually described in reports.21
These very divergent measurements were one of the reasons we called for a new photogrammetry
survey of the chamber so that a true and accurate survey of the space could be produced.22 The
ScanPyramids mission that was launched in 2015 had promised to accomplish such photogrammetric
scans for the four biggest pyramids and to put the results online,23 but that goal was not achieved
and a lack of clarity remained.
New architectural survey using photogrammetry
French lm maker and producer François Pomès is director of a series of TV documentaries
focusing on the great pyramids. In 2018, he contacted me regarding the architecture of the
monuments and expressed his interest in studying and recording them with photogrammetry. The
digital imaging project was to be carried out by the French company Iconem, with the agreement of
the Egyptian authorities. The goal was to y cameras suspended from a drone over the structures, at
close proximity. As a comprehensive survey was too time consuming, the team members followed
my suggestions in order to focus their attention on locations where architectural information with
particular value could be gathered. Although it would not utilize the drone, I also directed them
to target the upper chamber of the Bent Pyramid, which could be photographed from inside at all
angles,24 providing an accurate architectural survey of the space for the rst time.25
3D digitisation of archaeological sites has been in use for around 20 years, but its application has
typically implied high costs. In the last few years, thanks to photogrammetry, the technique has
become simpler, less costly, and as a result it is more widely used. It is now the most effective and
cheapest method of carrying out three-dimensional survey of large structures. Implementation
consists of accurately locating every point of a three-dimensional object in space, using a large
number of detailed photographs that are taken from different angles. The result is a dense point-
cloud that recreates a 3D model of the object and includes textural information derived from the
external appearance of the object of interest. The method is particularly valuable for describing
complex and irregular structures like a cave or a ruined building. It was, therefore, particularly
appropriate for the documentation of the upper chamber of the Bent Pyramid, the accessibility
and condition of which have always made its description very challenging.
18 Monnier and Puchkov (2017), pp. 60-61.
19 Dormion and Verd’hurt (2016).
20 Monnier (2017b).
21 Dormion and Verd’hurt (2016), p. 157-165.
22 Monnier and Puchkov (2017), p. 60.
23 http://www.scanpyramids.org/assets/components/pyramids/pdfs/About_ScanPyramids-fr.pdf.
An overview of the mission’s activities from 2015 to 2018 can be found in Monnier and Lightbody (2019), pp. 192-194.
24 It was not possible to safely access the bottom of the room, inside the wooden framework. Photos were shot from the top of
the platform.
25 A preliminary presentation of the results was published in Nile Magazine (See Monnier (2019)).

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Fig. 4. 3D digitization of the upper chamber of the Bent Pyramid using photogrammetry.
General perspective view toward the North-East (© Label News).
Our initial survey of the space showed that it has a complex formation history. It underwent
many changes during its construction, but also experienced some damage over time, and partial
dismantlement by a succession of archaeologists in the mid-20th century (see above). Based on the
surveys made by Maragioglio and Rinaldi, the rectangular plan of the chamber is 5.26 meters wide
(E-W) by 7.97 meters long (N-W).26 Due to the difculty of taking 3D images inside the wooden
structure and close to the oor level, we were unable to obtain results with a sufcient precision
for checking, correcting, or improving on these values.27
26 Maragioglio and Rinaldi (1964), tav. 13.
27 It would seem that it is longer than previously estimated.

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Fig. 5. 3D digitization of the upper chamber of the Bent Pyramid using photogrammetry. Perspective
view looking toward the top of the vault, North being to the left (© Label News).
Fig. 6. 3D digitization of the upper chamber of the Bent Pyramid using photogrammetry.
Perspective view looking toward the north wall (© Label News).

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Monnier, A new survey of the upper chambers of Snefru’s pyramids at Dahshur
Pl. 1. Section views of the Upper chamber of the Bent Pyramid at Dahshur. Scale 1:100.
(Franck Monnier)
Updated perspective view of the upper arrangement.

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The chamber is covered with a high corbelled vault for protecting it from the mass of the pyramid
above. According to Fakhry, there were sixteen overhangs and the room was 16.50 meters high.28
Dormion stated that there were fourteen overhangs and the height was only 13.90 meters.29
It is extremely difcult to discern the levels of the overhangs and to assess their overall number on
the basis of traditional photography alone, or indeed by in-situ observation, but the new 3D scan
allowed us to determine with certainty that the number is fteen, which is the same number as are
found in the lower chamber.30 In addition, the vault rises by around 11 meters, which is another
point this space has in common with the lower chamber. The photogrammetry also let us correct
the total height of the room to approximately 14 meters (+/- 0.1 m)31 and not 16.50 meters,
thereby conrming the measurement published by Dormion in 2016.32
28 Fakhry (1959), p. 52.
29 Dormion and Verd’hurt (2016), pp. 157-165.
30 Maragioglio and Rinaldi (1964), tav. 12.
31 This range of uncertainty is due to the non-at shape of the top course and the rough condition of the dismantled oor.
32 Ibidem.
Fig. 7. Reconstruction of the three construction stages of the upper chamber (section view, toward the
North) in the Bent Pyramid according to Franck Monnier and Alexander Puchkov
(drawing: Franck Monnier).

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We originally suspected that the stepped recesses of the vault were twice re-cut by the builders up
to the ninth corbel.33 The study conrmed our observations, but showed that the cutting continued
even higher, up to the tenth overhang.
After the clearance of approximately three quarters of the masonry lling, Abd el-Salam Hussein
revealed the existence of a substantial wooden shoring structure that was entirely hidden in the
masonry mass. Two kinds of beams could be distinguished: the vertical ones, which are placed
against the western, northern, and eastern walls; and horizontal ones propping up the side posts,
which were all aligned along an east-west axis. The ends of the horizontal shoring beams are neither
fastened nor embedded in any manner, but are simply held in vice-like compression between the
two walls.
The rst four overhangs also have a few surviving end fragments of cross beams embedded in the
walls, as well as sockets and other traces showing that beams were used in those locations. One of
them remains in a higher corbel.
Construction chronology and defect diagnosis
The wooden framework probably had no other purpose apart from to counteract the lateral
thrusts from any wall movements. The kind of thrust it was designed to counter would not have
been strains caused by structural failure and it was probably not installed to prevent a structural
disaster.34 It would have been useless for resisting such strains and this frequently mentioned
hypothesis should be avoided. According to my studies, the existence of the wooden structure
can be explained by the fact that the walls of the room, including the corbelled courses, had to be
supported for the few months or years that were required to raise them.35
The builders seem to have erected the four walls using carefully cut ashlar masonry set up around
the wooden shoring framework. They then laid the more roughly cut stone blocks of the pyramid’s
core against its exterior sides. The internal bracing would have been used to prevent small sliding
movements of wall stones when they were still insufciently loaded to lock them in place. This
method is evidenced at the overhangs, where traces of circular cuts can be seen facing each other,
between which wooden propping beams were held in place during the installation of the stone
blocks. Other roughly squared logs were deeply embedded at some levels. As these elements are
only recorded inside the vault section, it is very likely that they were designed to support platforms
on which the workers could carry out the nal dressing of the overhangs more easily.
It is, therefore, fundamentally important to differentiate between the different structural elements
observed in this room, and to identify their different functions. The shoring of the lower part of
the chamber ensured the strength of walls during their construction. The shoring beams associated
with the vault stone courses, of which only traces remain on the stones, had the same role. Additional
props supported working platforms for carrying out nishing work under the vault. The lower part
of the chamber was not furnished with such embedded propping beams.
But why did they bury the temporary wooden structure into the masonry mass installed in the
lower volume of the chamber?
In answer to this question, research scholars have often put forward the idea that the surrounding
masonry was behaving unpredictably and that the walls experience a bulging that the Egyptians
33 Monnier and Puchkov (2016), pp. 21-24.
34 A frequently expressed view (Edwards (1985), pp. 86-87 ; Verner (2001), p. 177 ; Vyse (1842), p. 68).
35 Monnier (2017a), p. 92.

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had to counteract by lling the room with masonry.36 In this scenario the wooden framework
would have been a prelude to more drastic measures that eventually culminated in the permanent
abandonment of the space.
There are a number of arguments against this point of view. First, almost the entire support structure
was dismantled, so no signicant failure or settlement in the upper chamber had occurred by the
time the removal was halted. Second, any lateral thrusts would not have been restricted to the lower
half of the chamber, but to the whole volume. If the motive of the builders was to strengthen the
chamber by lling it with masonry then they should have lled the entire volume (if that was their
motivation then the whole structure was in danger of collapsing), but that was not the case.
During our study we noticed additional details of crucial importance that led us to understand the
real intentions of the builders.37 Italian architects Maragioglio and Rinaldi had previously identied
two construction phases that led to the creation of the masonry mass.38 First, the oor was raised
to a height of 3.46 meters and paved over with well-dressed stone slabs (g. 3). We were able to
establish that great care was taken to conceal the rst overhang during this work. A row of thin
stone blocks was inserted under the edge formed by the recess, and the next three overhangs
above it were re-cut. The adjustments are very clear, as many chisel marks are still visible in several
locations on the walls. The result was the attening of the rst stone courses of the vault, and as
a consequence the vertical height of the side walls was increased. The stones on the south side of
the mass were carefully laid and dressed so as to let a passage extend out into the horizontal access
corridor. When the evidence is taken together, it is clear that the purpose of the exercise was not
to avoid a disaster but to raise the level of the oor up by more than 3 meters. The chamber could,
therefore, continue to be used as a burial place. This phase of work occurred before the removal of
the remaining shoring devices, and therefore took place during an early stage of the construction.
Modications did not stop there. In a second phase of activity, the builders decided to elevate the
oor once again by doubling the height of the existing mass. Again, it was covered with limestone
paving slabs, and the builders re-cut ve overhangs so as to give a homogeneous and smooth
appearance to the side walls. One of the recesses was partially cut in order to be integrated into the
new and denitive oor (the current ‘cornice’).
In order to reach the top of the platform, a temporary staircase was built with very rough stones,
This lled the southern part of the room and it was still there before the rst excavations began in
1947. Its presence apparently required the entrance passage’s roof to slope up, probably to facilitate
the passage of the funeral procession and its bulky funerary furniture.
Abd el-Salam Hussein photographed the space before searching for the hypothetical buried
sarcophagus. One of his photos shows a mound of rubble and stone fragments that had fallen
from the upper part of the vault onto the oor. The clay-seamed nature of the limestone made it
susceptible to signicant levels of fragmentation. A full engineering material study remains to be
done, but the state of the materials and the structure allow me to share some initial thoughts about
its design and construction.
The overhanging inside corners of such a corbelled vault are subjected to shearing stresses whose
magnitude depends on the depth of the overhangs. The degradation that is visible, which may have
begun to appear as early as during Snefru’s reign, would gradually have increased in severity, and this
36 See note 32.
37 Monnier and Puchkov (2016), pp. 21-24.
38 Maragioglio and Rinaldi (1964), pp. 70-72.

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could have been accelerated by the reshaping of the recesses. Moreover, visible repairs carried out
with gypsum mortar show that the stones responded badly to the recut. Photographs clearly show
two distinct areas on the surface covering: attened overhangs and more seriously damaged ones.
Smooth surfaces that were not subjected to localised stresses remain in much better shape, however,
they also suffered more minor losses. That could be due to the particular nature of the stone.
It seems that the limestone blocks exhibit fracturing perpendicular to their upper/lower surfaces
and that this is almost certainly the result of something inherent in the rock from before it was
quarried. When initially extracted, these fractures were closed or sealed and so presented no problem
for the builders. A rock under a load will, however, expand over time (due to stress release) in the
direction of an unconned surface, and this would have happened to the limestone blocks lining
the vault. As those blocks expanded, the formerly closed fractures opened up with the result that
very ne chips, akes, or other pieces of the blocks spall off. This same phenomenon is commonly
seen in the bedrock walls of underground mines and deep road cuttings.39
The lower side of the eleventh overhang was enlarged by the recut of the lower recess. It is likely
that this signicant cantilevered section eventually broke, resulting in a heterogeneous diffusion of
stresses that was dependent on the form of the modications made to the structure. Over time, a
natural vault effect occurred. For that reason, the peak within the stone roong now looks like a
natural grotto or cave.
In terms of an architectural pathology, photogrammetry allowed me to identify the existence of
opened ssures and other breaks in the stone under the uppermost, well-shaped, corbels (g. 8).
The overhang of the twelfth one, which is particularly large, exposes these overhang blocks to
more cracking, and large fragments could fall down. It is impossible to estimate when this might
occur, but the risk is real.
This photogrammetry survey thus led us to signicantly update the body of knowledge currently
available regarding the upper chamber of the Bent Pyramid. Although it is the central element
39 I am extremely grateful to geologists James A. Harrell and Stuart L. Dean for sharing their reections about this with me.
Fig. 8. Highlighting of opened ssures (in red) in the twelfth corbel (left: view toward the
South; right: toward the West) (© Label News).

JAEA 4, 2020
Monnier
14
of the monumental building, it was previously understood quite supercially. I hope that these
results will encourage the authorities to grant permission for the launch of a more complex
photogrammetry project and the establishment of a team able to undertake a comprehensive
survey of the monument. This would culminate in the publication of a fully accurate architectural
report in accordance with modern archaeological requirements.
The upper chamber of the Red Pyramid
Early descriptions
Little attention was paid to the funerary chamber system within the Red Pyramid after its initial
exploration, which was carried out at the beginning of the 19th century by John Shae Perring. He
gave this brief description:
‘The third chamber is 27 feet 3 ½ inches (8.30 m) long from east to west, and 13 feet 7 ½ inches
(4.14 m) wide from north to south. The sides are perpendicular for 12 feet 1 inch (3.68 m), after
which fourteen courses project inwards, as in the other apartment ; and the total height from the
original oor to the ceiling, is 48 feet 1 inch (14.62 m).’40
In the mid-20th century, a scientic study of the Red Pyramid was planned by Abd el-Salam Hussein
and Ahmed Fakhry, but neither of them published a report of their work. In the 1960s, Vito
Maragioglio and Celeste Rinaldi produced the most detailed architectural report of the monument
to date.41 It currently represents the main reference source for those who want to study the Red
Pyramid’s architecture and chamber layouts. Their dataset was fairly standard in format and no
more surveys have been undertaken since then, which could provide more information about the
inner chamber and passage arrangements.42 The burial chamber was described using these words:
‘Our measurements, except for a few centimeters, conrm Perring’s. The main axis of the crypt is in
an E-W direction and thus at right angles to those of the preceding chambers. The north and south
walls are vertical for about 3.70 m. and then there are 14 courses which form a corbelled vault.’43
From my own observations, I suspect that the Italian architects partially reproduced Perring’s
survey, especially with regard to the upper chamber, without having taken the time to verify them.
Towards an updated description
An analysis of photographs I took in 2012 indicated that there were inaccuracies in the existing
reports. Some shots showed that the number of corbels was not 14, but 13. As I was not able to
make new measurements in-situ to check this detail, I could not yet properly support a proposal to
update the reports. The photogrammetry survey carried out in fall 2018, however, has allowed me
to conrm my preliminary observations, but also to draw new sectional views of the chamber. Not
only was the number of corbels wrong until now, but the height of the room was also inaccurate.
It is not 14.67 meters high,44 but around 13.68 meters high. This is an error in excess of one meter,
and similar to the level of error that I had already detected in the Bent Pyramid’s survey.
40 Perring (1842), p. 16.
41 Maragioglio and Rinaldi (1964).
42 An illustrated description of the interior has recently been published (Haase (2019)).
43 Maragioglio and Rinaldi (1964), pp.130-132.
44 Maragioglio and Rinaldi (1964), tav. 19.

JAEA 4, 2020
A new survey of the upper chambers of Snefru’s pyramids at Dahshur
15
Fig. 9. 3D digitization of the upper chamber of the Red Pyramid using photogrammetry.
General perspective view toward the South-East (© Label News).
Fig. 10. 3D digitization of the upper chamber of the Red Pyramid using photogrammetry.
Upper view of the excavation, North being at the top (© Label News).

JAEA 4, 2020
Monnier
16
Fig. 11. View of the upper chamber of the
Red Pyramid toward the west.
(photo: Franck Monnier)

JAEA 4, 2020
Monnier, A new survey of the upper chambers of Snefru’s pyramids at Dahshur
Pl. 2. Section drawings of the upper chamber of the Red Pyramid at Dahshur. Scale 1:100.
(Franck Monnier)
Inside arrangement of the Red Pyramid in its original condition.
Scale 1:500.

JAEA 4, 2020
A new survey of the upper chambers of Snefru’s pyramids at Dahshur
17
For the rst time, the excavation made by looters in Antiquity into the oor of the room is published
with a great accuracy. Explorers from ancient times also dug the beginnings of a tunnel into the
northern wall. I don’t venture an explanation for why they suspected the existence of a room or a
passage in that direction, but in any event, they quickly abandoned the attempt.
The newly established photogrammetry survey of the Red Pyramid, with its detailed section and
plan views, clearly shows the effectiveness of this imaging method.
Conclusion
Both of these projects at Dahshur have demonstrated the effectiveness of the photogrammetry
imaging method. It is economical, accurate, and rapid. The argument for undertaking a more
comprehensive survey of the entire inner chamber system is now clear. This would allow us to record
the state of the monuments in order to manage their structural conditions as they develop over
time. It would also allow us to draw a complete set of accurate plans and provide a comprehensive
description of the pyramids for the rst time. The technology is now available to produce survey
reports that can do justice to these extraordinary monuments.
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