Sanctuary of Zeus at Nemea developed in the beginning of the 6th century BC, with the institution of the Panhellenic Nemean Games in a region where human activity had been present since prehistoric times. The first temple of Zeus and the first two phases of the Heroon were constructed during the Archaic period while nine "Oikoi-Treasuries" were erected in the 5th century BC. At the end of the 4th century BC, a new temple of Zeus, baths, a hostel, a Stadium and the 3rd phase of the Heraion were built as part of a large construction project. After the transfer of the games to Argos, in 270 BC, the sanctuary fell into decline. During the 5th and the 6th centuries AD, a small community grew in the vicinity and a basilica was erected on the ruins of the hostel. This community was dissolved during the raids of the Slavs in 580-590 AD.
The first, small-scale excavations were carried out in 1766 by the mission of the Dilettanti and were continued in 1884-1912 by the French School of Archaeology at Athens. Between 1924 and 1926, investigations on the site were undertaken by the Americal School of Classical Studies, with the excavations of the Sanctuary and the hill of Tsoungiza by H. Hill and C. Blegen. Following a long interruption, C. Williams, brought to light in 1964 part of the "Oikoi-Treasuries", of the hostel and a kiln. Extensive and systematic excavations on the site were carried out from 1973 to 1986 by the University of Berkeley at California, under the direction of S. Miller.
Stadium of Nema, which could accomodate 40.000 spectators, was built 400 m SE of the Temple of Zeus. The track (total length of 178m) was bordered by a stone water-channel with stone
basins at intervals for drinking water. The stone starting line was on its western extremity. A rectangular building with an internal colonnade on its western side served probably as a "changing room". From it, the athletes and the judges entered the Stadium through a vaulted tunnel. The spectators sat in roughly levelled terraces (degrees), cut in the soft rock, while two or three rows of seats were constructed between the starting-line and the stoas.
The Stadium in which Panhellenic games were held every two years in
honour of Opheltes, was built at the end of the 4th century BC, as part of a renovation project of the Sanctuary. In about 270 BC, the games were transferred to Argos. Despite an attempt in 235 BC of Aratos of Sicyon to bring them back to Nemea (and indeed, for a while, they took place alternately in Nemea and Argos), the games were definitively transferred to Argos not long after.