After the fall of Alexander the Great, the Seleucid ruler, Antiochus 1, built a new city here which he called Anthiochia Margiana.  The picture on the right shows the brick formation - rather than tessellating single bricks, the walls were built with three or four individual bricks in parallel. The building on the bottom right might have been the equivalent of a post office - inside are numerous niches which could have been pigeon-holes - well it's one theory anyway.