Which is the oldest man-made structure in the world?
Also in Japan is evidence of the world's oldest known structure, though post holes don't really make much of a building. They are from about 500,000 years ago.
In Malta there is the Neolithic temple of Hagar Qim, dated to around 3000 / 3500 BCE, and the Hypogeum there dated around 2500BCE.
Stonehenge dates to around 3500-5000 BCE.
Newgrange was built around 3200 BC, during the Neolithic period
The oldest pyramid is the Djoser Step Pyramid at Saqqara, Egypt, was constructed by Imhotep 2630 BCE.