Summary A preliminary report is given on the copper-smelting site HLO-1 of the Umm an-Nar (Umm al-Nār) period in upper Wādī al-Дilo in Sharjah, UAE. Two seasons of explorations by a joint team of the Sharjah Directorate of Antiquities and the University of Tübingen (Germany) in 2007 and 2008 yielded evidence for an Islamic settlement and graveyard at the site, as well as living structures, a ... [Show full abstract] fortified building (watchtower), and a copper-smelting workshop of the Early Bronze Age. A large hemispheric ingot of pure copper testifies to metal production at the site. From the amount of slag found during the explorations, a total of up to 56t of locally produced copper could be estimated. The slag is of the Fayalite type and differs slightly from the slag analysed at the contemporary site of Maysar 1 (Oman). The difference may be due to the local ore, which was extracted from a vein situated at the slope above the site. The melting temperature of the slag from Wādī al-Дilo was determined to have been about 1200°C. Most of the prehistoric pottery found at the site is from the Umm an-Nar period. A few sherds and a radiocarbon date also indicate an occupation during the Wādī Sūq period.