The prehistoric settlement at Ayia Irini. The ruins of the prehistoric settlement at Ayia Irini can be seen on the northern side of the Ayia Irini peninsula. The site was inhabited from Neolithic times through the 15th century B.C. when, according to historical sources, it was destroyed by a severe earthquake.
Ancient Carthaia. Carthaia was one of four cities that flourished on Kea in antiquity. The most important ruins in the area are:
- The fifth-century-B.C. temple of Apollo marked by six decorated columns
- The temple of Athena, built in the late sixth century to early fifth century B.C. Fragments of a sculptured pediment with scenes from the battle of the Amazons have been unearthed at the site.
- Ayia Marina Tower. The Tower of Ayia Marina is located in Kea's interior, between the sites of ancient Coryssus and Poiessa. It was built during the Hellenistic period and is a typical example of a detached fortified tower.
- The Monastery of Panayia Kastriani perched on Kastri hill.
- The Lion of Tzia sculpted into a rock over Ioulida. The lion figures in a number of local legends.
- The restored stone windmills at Koundouros.
- The Town Hall at Ioulida, a neoclassical building erected in 1902 and decorated with ceramic sculptures of Apollo and Hermes.
- The public school at Ioulida, a neoclassical building designed by the Bavarian court architect Ernst Ziller.
- Paintings by Alekos Fassianos on one of the shelters in the capital's main square.
- The acropolis of ancient Ioulis with visible ruins of the temple of Apollo and medieval fortifications added in the 13th century.