Göbekli Tepe
Construction

The plateau Göbekli Tepe is situated on has been shaped by erosion and quarrying from the Neolithic onwards. There are four 10-metre-long (33 ft) and 20-centimetre-wide (7.9 in) channels on the southern part of the plateau, interpreted as the remains of an ancient quarry from which rectangular blocks were taken. These are possibly related to a square building in the neighbourhood, of which only the foundation is preserved. Presumably, this is the remains of a Roman watchtower that was part of the Limes Arabicus, though this is conjecture. Most structures on the plateau seem to be the result of Neolithic quarrying, with the quarries being used as sources for the huge, monolithic architectural elements. Their profiles were pecked into the rock, with the detached blocks then levered out of the rock bank. Several quarries where round workpieces had been produced were identified. Their status as quarries was confirmed by the find of a 3-by-3 metre piece at the southeastern slope of the plateau. Unequivocally Neolithic are three T-shaped pillars that had not yet been levered out of the bedrock. The largest of them lies on the northern plateau. It has a length of 7 m (23 ft) and its head has a width of 3 m (10 ft). Its weight may be around 50 tons. The two other unfinished pillars lie on the southern Plateau.

Archaeologists disagree on how much labour was needed to construct the site. Schmidt maintained that "the work of quarrying, transporting, and erecting tons of heavy, monolithic, and almost universally well-prepared limestone pillars was not within the capability of a few people". Using Thor Heyerdahl 's experiments with the moai of Rapa Nui as a reference, he estimated that moving the pillars alone must have involved hundreds of people. According to these experiments, one moai of similar size to a T-shaped pillar from Göbekli Tepe would have taken 20 people a year to carve, and 50–75 people a week to transport 15 km. Schmidt's team has also cited a 1917 account of the construction of a megalith on the Indonesian island of Nias, which took 525 people three days. These estimates underpin their interpretation that the site was built by a large, non-resident workforce, coerced or enticed there by a small religious elite. However, others estimate that just 7–14 people could have moved the pillars using ropes and water or another lubricant, with techniques used to construct other monuments such as Stonehenge. Experiments at Göbekli Tepe itself have suggested that all the PPNB structures currently exposed could have been built by 12–24 people in less than four months, allowing for time spent quarrying stone and gathering, and preparing food. These labour estimates are thought to be within the capability of a single extended family or village community in the Neolithic. They also match the number of people that could have comfortably been inside one of the buildings at the same time.

Enclosures B, C and D were initially planned as a single, hierarchical complex that forms an equilateral triangle, according to Haklay and Gopher.
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