Yeronisos, or as it is often called " Sacred Island ", is 12,000 square meters of rocks, rising dramatically from the swelling seas just 280 meters from the harbor at Saint George. Excavations show that Yeronisos had an active Chalcolithic phase (3100 B.C.) and flourished under the ruling of the famous Egyptian Queen Cleopatra (50-30 B.C.).

Coins, pottery, glass, inscriptions, and unique architectural remains suggest that Yeronisos preserves one of the most significant Ptolemaic sites outside Egypt. An earthquake seems to have devastated the island during the late 1st century B.C./early 1st century A.D. after which it remained abandoned, aside from some squatters' activity, until the 6th century A.D. It was then when a reservoir with impluvium and animal shelters were built.