In the ancient times Leros and Kalymnos were called Kalyndia. The name Leros is presumed to come from the word “levros” which means smooth, because, unlike the mountainous and rocky Kalymnos, Leros has a smooth and fertile soil.
Leros was inhabited since the 3rd millennium BC. The first inhabitants were Carians, Leleges, Phoenicians and Cretans (Minoans). Leros like all the Dodecanese, participated in the Trojan War.
In the 11th century BC the Dorian settled and in the 6th century the Ionians came from Miletus, who according to Herodotus, brought a new culture to the island. This very important period ended in 454 BC with the conquest of the region by the Persians.
After the defeat to the Persians, Leros participated in the Athenian League. In the years that followed, Leros changed rulers until it was liberated from the Persians by Alexander the Great, whose presence marks the transition from the classical to the Hellenistic era, proved by tombstones with Macedonian names and coins.
In Roman times the strategic importance of the island was confirmed by Plutarch. In the main village of the island, at that time called Leros and and located at today's Agia Marina, are remains of the Roman fort 'Broutzi ", as well as ruins of an aqueduct with arched stonework and architectural parts of a temple, probably dedicated to Asclepius.
Leros, due to Byzantine period (at the end of third century and after) has remarkable samples of ecclesiastic architecture and fortifications. During this period, the castle of Panteli was built. It is the most important medieval monument of the island and overlooks the settlements of Agia Marina and Platanos. It has a remarkable view over the Aegean. You can see until today the three precincts of the castle (the two internal are dated before 1087). The church of Our Virgin Mary at the Castle was built in the late 17th century. It is accessible via traditional stairs and modern road.
At the village Platanos, until mid last century, important aqueduct discoveries of the decade in 1730 were saved, built on the ruins of the Roman aqueduct that brought water from the source of Paliaskloupi Meroviglia to the city. In 1887 it stopped to operate and was demolished. In 1309 Leros was occupied by the Knights of St. John of Rhodes, who ruled despotically until 1523.
During this period Leros was used as a place of exile. In 1523 Leros was enslaved by the Turks but maintained a relative independence, keeping privileges as autonomy and self-government by paying taxes to the sultan.
In 1821 Leros, enabled by the autonomy it had from the Turkish power, took an active part in the Greek Revolution with local warlords Krasouzis, Tourkomanolis, Chatzimanolis, and it became part of the Greek state, as all the Dodecanese. But, by the London Protocol of 1830, the Dodecanese islands were granted to Turkey again and Leros falls back to the Turkish occupation.