Lording over the seafront, the Castle of St. Peter is at the top of every visitor's things to do in Bodrum list. The Knights Hospitallers of St. John built the structure between 1402 and 1437, and knights of the various nationalities of the order were entrusted with the defense of particular sections of the walls.

Among the various towers are the French Tower; English Tower, with a sculpted lion on its west wall; and the Gatineau Tower, which leads to the dungeons. During the reign of the Ottoman sultan Süleyman the Magnificent, the castle passed into Turkish hands and a mosque was built inside.

Today, many of the vast halls inside the castle display the exhibits of Bodrum's Museum of Underwater Archaeology