The Bodrum Castle (Castle of St. Peter or Petronium) was built by the Knights of St John between 1406-1522 on a small rocky peninsula set between two sheltered harbors in Bodrum. In the construction of the castle, the stones of Mausoleion, which was one of the seven wonders of the world and demolished due to an earthquake were used. The Bodrum Castle (Castle of St. Peter or Petronium) has towers known as the French, Italian, English, German and Spanish (The Snake Tower) bearing the names of the nations responsible for their construction. After the island of Rhodes was taken over by the Turks in 1522, the knights left Bodrum and its surrounding territory on January 5., 1523. Being used as a prison for a period of time since 1895, the castle turned to ruin due to bombing of the French and English forces on May 26-28, 1915, during World War I. and was abandoned.
Except the the walls of the castle on the east side, those on the other sides were fortified as double walls. There are seven gates leading to the keep inside the castle and studded coats of arms above the Gates of the moats. There are crucifixes, flat - horizontal belts, dragon and lion figures on the coats of arms. Including the basement of the chapel, there are 14 cisterns in the inner stronghold. The castle pillbox, the ditch between double walls, drawbridge, watch tower and the tughra of Sultan Mahmut II. are marvels to behold in the castle.
During the period of that the Bodrum Castle was used as a prison at the end of the 19th century, it was ascribed Ottoman character with the addition of a turkish bath.Today The castle is used as the ‘Museum of Underwater Archaeology’.