The island of Spinalonga, officially known as Kalydon, is located in the Gulf of Elounda in north-eastern Crete, in Lasithi, next to the town of Plaka. 

Originally, Spinalonga was not an island – it was part of the island of Crete. During Venetian occupation the island was carved out of the coast for defence purposes and a fort was built there.

During Venetian rule, salt was harvested from salt pans around the island. The island has also been used as a leper colony. 

Source: Wikipedia