The island of Telendos was joined with Kalymnos until the middle of the 6th Century A.D.
The powerful earthquake of 554 A.D., which struck th entire East Byzantine Empire, also mortally affected Kalymnos, causing deaths, destructions of settlements, churches and subsidence. The region between Kalymnos and Telendos sunk in the sea.
Evidence o this destruction are the enormous cracks at the coast of Kalymnos, opposite Telendos, as well as the sunken buildings at the east coast of the island of Telendos and in the bottom of the marine channel, between Telendon and Kalymnos. At Pothia Beach, one half of a church is found on dry land while the other half is underwater.
Walking alongside the sea on the east coast of Telendos, it is still possible to see the remnants of the sunken buildings at the bottom of the sea.