An open-air cult, that lasted from the Mycenaean times (1300 - 1100 B.C.) until the Middle-Geometric II period (800-750 B.C.) was succeeded at Iria by a worship housed in four superimposed buildings, found in successive layers, at exactly the same site and with the same orientation.
The first was built around 800 B.C. and it consisted of a single room constructed of wood and bricks. A probable flooding of the nearby river Byblines (today known as, the Peritses) destroyed this first building. Around 730 B.C. it was replaced by a hall intended for mysteryrites, with four aisles defined by colonnades. Around the walls were benches for the worshippers.
After the destruction, for unknown reasons, of this second temple, a third building was erected in c. 680 B.C., at the same site, using same of the earlier walls. This had three aisles and an early form of tetrastyle portico.
This too was short-lived. Around the end of the 7th century B.C., the cult was again carried out in the open-air, the focus being a four-sided clay hearth. It was found practically intact, and it is visible beneath the marble threshold of the later adyton.
Around 580-570 B.C., work began on the fourth and largest temple of all, the only one of which remains are visible, and the only one to have been restored. It is an archaic hekatompedon of Ionic style. It is built of local grani-diorite rock, and it has an adyton (for a mystery cult), marble portico (prostasis) with columns forming a monumental entrance, and a marble altar. Owi tetrastyle marble colonnades divide the building into three aisles.
The instability of the subsoil and the fact that the builders had as yet little experience in setting the foundations for such a big temple, necessitated repairs on a vast scale during Roman times (1st century B.C.). During the 5th century A.C., the temple was converted into an Early Christian basilica. The foundation of the little Byzantine church of St. George in the immediate vicinity of the ancient temple has ensured the continuity of worship in this same place for 3,300 years.
In late antiquity the sanctuary was surrounded by a spacious rectangular enclosure wall (temenos), measuring at least 70 ? 58 m. which on the west incorporated a stoa-like construction (two square rooms with a stoa in front of the entrance).
Continuation of the excavation during the past two seasons has shown that this is a ceremonial dining-hall (a building for communal feasting during the festival). The earlier, apsidal building phase of the dining-hall goes back to the early archaic period (7th century B.C.). In the classical phase (4th century B.C.) it could accommodate at least eighteen distinguished people who dined reclining on couches, while the rest of the worshippers dined in the open-air. The entire area produced a plentiful amount of pottery, both cooking and table-ware.