Between the Treasuries and the Classical Temple there is one of the most unique buildings of ancient Greek architecture. The popular Tholos with a circular shape. The reason they constructed this building and other similar buildings in other Greek sanctuaries like in Epidaurus and Olympia is still unknown since we don't have any information about it. The oldest theories about its shape link the building to the cult of a local deity whereas modern theories suggest that it was another treasury. It was built at the beginning of the 4th century BC according to plans by the architect Theodoros. It was made from the marble from Mount Penteli and it was surrounded by a colonnade of 20 doric columns. The wall was a stepping in floor made of grey marble from Elefsina. In the interior there was a mantle along the base of the wall also from grey marble which supported 10 Corinthian style semi columns. The variety of materials, colors and styles along with the contrast between the vertical columns and the curved lines of the wall contributed to a remarkable overall composition. The building also had rich decoration with reliefs depicting the mythological battles of the centaurs and the amazons. It is partially reconstructed.