Due to its strategic location, Gramvousa was fortified by the
Venetians, who built a well-fortified
castle on the top of a steepy rock at an altitude of 137 m. Construction on the castle of
Gramvousa started in 1579 and ended in 1582. It was destroyed in 1588, however, when thunder struck on the powder store.The castle was rebuilt in 1630. It was one of the three castles to remain under Venetian dominion after the Turkish occupation of
Crete (the other two were those of
Sitia and
Spinalonga. Even though the castle was impregnable, during the Venetian-Turkish war the Italian commandant was bribed by the Turks and he gave over the castle in 1692.