After fifteen years of excavation at Göbekli Tepe, researchers led by Klaus Schmidt of the German Archaeological Institute (DAI) have excavated four circular enclosures, dated to the Pre-Pottery Neolithic A period. A geomagnetic survey in 2003 identified perhaps as many as sixteen more round or oval enclosures at the site.
The earliest buildings at Göbekli Tepe were circular rooms each with a diameter of over 20 meters and constructed of stone quarried from nearby sources. The buildings are made up of a mortared stone wall or bench, interrupted by 12 stone pillars each 3-5 meters high and weighing up to 10 tons each. The pillars are T-shaped, pecked out of a single stone; some of the surfaces are carefully smoothed. Some have pockmarks on the top.
Differences between the four PPNA enclosures have been identified, and the excavators believe that Göbekli Tepe was used by four different cultural groups: the building form and overall design is the same, but the iconography is different in each one.
Alternative Explanations
In his Current Anthropology article, Banning points out that the main argument that these are cultic structures are that they lacked roofs. If indeed these buildings lacked covering, that would make them unsuitable for living: but Banning believes that the T-Top pillars were roof supports. If the terrazzo floors had been exposed to the weather, they would not be as well-preserved as they are currently. Plant remains recovered from Göbekli Tepe hint at roof covering, including the charcoal of ash, oak, poplar and almond, all of which grow sufficiently large to represent crossbeams for roofs.
