Ancient Eretria is the most important historical site on Evia. At one toe the city rivalled Halkida for dominance of the island, befeor Hlakida took power in the seventh century BC.

Unfortunately for the archaeologists, modern Eretria has grown up on top of the ruins of the ancient city, instead of on a nearby site as often happened.

Displays in Eretria’s own Archaeological Museum include a fearsome Gorgon’s head, retrieved from a villa of the fourth century BC. Nearby is the House of Mosaics, a restoration of a fourth century house with well preserved floor mosaics; the key is held at the museum. A cluster of other remains in this northwest corner of the town includes the theatre, which is particularly interesting for a passageway under the stage.