This is for the benefit of those that haven't yet seen the subsurface radar scan of Gobekli Tepe. The above image is from Deitrich et al., Antiquity vol. 86 (2012), freely available on the internet.The little portion of Gobekli Tepe so far excavated corresponds to the detailed portion of the map, bottom right, which includes the main circular enclosures A to D.The structure right in the middle of the plot looks especially interesting - being nearly twice the diameter of enclosure D. Considering the progression of these structures -But some of the other structures remaining in the ground also look to be massive.