Thanks to Kevin T. Glowacki and Nancy L. Klein

This is the west (back) end of the Parthenon as seen from the Propylaea. The large interior chamber of the Parthenon was divided into a main room, where Pheidias colossal statue of Athena could be found (in east end of temple), and a smaller chamber (in west end) which served as a treasury for the funds of the Delian Confederacy that were transferred to Athens.