Bodrum Castle (Turkish: Bodrum Kalesi) is a historical fortification located in southwest Turkey in the portcity of Bodrum (37°1′54″N27°25′46″E / 37.03167°N 27.42944°E), built from 1402 onwards, by the Knights of St John as the Castle of St. Peter or Petronium. A transnational effort, it has four towers known as the English, French, German, and Italian towers, bearing the names of the nations responsible for their construction. The castle was completed in the late 15th century, only to be taken over by the Islamic Ottoman Empire in 1523. The chapel was converted to a mosque, and a minaret was added. The castle remained under the empire for almost 400 years. After remaining empty following World War I, in the early 1960s, the castle became the home for the award-winning Bodrum Museum of Underwater Archaeology (see below). In 2016 it was inscribed in the Tentative list of World Heritage Sites in Turkey.