 Since the stadium was not set like the Panathenaic Stadium structure at the bottom of a gully, but on a flat area of land (24 hectares), its five tiers of seats for 405,000 spectators had to be supported in the usual Roman manner by massive barrel vaults.The external façade of pink granite blocks, which would have risen to a height of about 90 metres, consisted of a series of arches 65 metres high resting on a podium of dark red granite.The arcade and podium again suggests a Roman, not a Greek, circus or stadium, which did not traditionally rest on a substructure.