The Great Altar of Apollo was dedicated by the Chians. Constructed in the 5th Century BC, it is made of white and grey/black marble and is aligned with the position of the old temple of 548 BC rather than the current temple. In 1920, the people of Chios re-erected the altar and restored it fully to accuracy in 1960. Between the altar and the temple is an esplanade bearing more bases which once were topped by various statues and votives.

The current ruins of the Temple of Apollo date from the 4th Century BC and are the third temple built on this site. The first temple was destroyed by fire in 548 BC and the second by an earthquake in 373 BC. The temple is of the Doric order with 6 columns on its narrow sides and 15 columns on its long sides. Of the sculptures on the pediments, made by the Athenians Prazias and Androsthenes, only Dionysos remains, now in the musuem.

Plataia base and Altar Temple of Apollo