The church of Agia Eirini (Saint Irene) is one of the most important mid-byzantine monuments of Icaria, built on the foundations of an Early Christian basilica, parts of which are still visible. The church was in the past dated to the 9th-10th c. AD, but recent studies suggest a later dating, in the 11th-12thc. It is a cross-in-square church of the simple four columned (tetrastyle) type. The cross arms have gable roofs and the dome, supported by four square built pillars, projects over their junction. A synthronon is preserved inside the trilateral bema apse. To the west side of the main church a narthex is adjusted, the western wall of which still preserves four columns belonging to a ruined portico. The roofs of the church are covered with natural slates. The masonry is not visible, because the walls are covered with plaster.