Ancient Aigeira was located east of the Aiges village. It was one of the most important cities of Achaea and of the Achaean League.

The city was built on Palaiokastro hill at an altitude of 650m with its citadel on top. Historians and geographers of antiquity like Pausanias and Strabo wrote about it. The inhabitants of Aigeira participated in the Trojan war. The city thrived until the 4^th century BC, and it thought to have been destroyed either by a powerful tidal wave or by a strong earthquake.

The most important monument is the theater of the city, dated from the 3^rd century BC. The proskenion (in front of the scene) was decorated by semi-columns. The drainage of the orchestra is still preserved as is the north wall of the skene with its main gate. The biggest part of the theater was destroyed in the 2^nd century BC when the skene became a three-storey building. The façade was divided into three storeys with protective roof: The Doric ground floor, the Ionic middle floor and the Corinthian top floor. Yet, few vestiges remain from the decoration of this three-storey building.

The temple of Zeus and the temple of Artemis were excavated next to the theater. The floor in the temple of Zeus is a mosaic made of pebbles from the river depicting vultures, scarabs, an eagle attacking a snake and two vases. The first finding brought to light by the excavations was the marble head of a statue of Zeus, which according to Pausanias was the work of the renowned sculptor Euclid from Athens. It must be noted that Aigeira circa 330 BC minted its own bronze coins.