The archaeological site of Olympia in Ilia district in Peloponnesus is situated in a valley, which has been inhabited since prehistoric times. In the 10th century before Christ a sanctuary was established here, which became a centre for the worship of Zeus. The Altis – the sanctuary to the gods – has one of the highest concentrations of masterpieces from the ancient Greek world. Ruins of numerous temples have been preserved in Olympia as well as the remains of the sports structures erected for the Olympic Games, which were held in Olympia every four years beginning in 776 before Christ.