The Altis (the sanctuary to the gods) includes the ruins of the two principal temples: the Temple of Hera (6th century BC) and the Temple of Zeus (5th century BC). The sanctuary contained one of the highest concentrations of masterpieces of the ancient Mediterranean world.In north-western Peloponnesos the archaeological site of Olympia at the foot of the Kronion Hill stretches over a triangular alluvial terrace at the confluence of the Alpheios and the Kladeos.