The fortifications of Heraklion are a series of defensive walls and other fortifications which surround the city of Heraklion (formerly Candia) in Crete, Greece. The first city walls were built in the Middle Ages, but they were completely rebuilt by the Republic of Venice. The fortifications managed to withstand the second longest siege in history for 21 years, before the city fell to the Ottomans in 1669.