Makronisos (Μακρόνησος, in Greek, lit. long island) is an island in the Aegean sea, in Greece and is located close to the coast of Attica, facing the port of Lavrio. It has an elongated shape (3km north to south, ca. 500 m east to west) and its terrain is arid and rocky. In ancient times. the island was called Helena.
Currently it is uninhabited, however, during the Greek Civil War, it was used as a concentration camp for Greek communists, hosting hundreds of prisoners. Because of its history, it is considered as a monument of the civil war era; therefore the island itself and the original structures on it are protected from alterations.