Bodrum Castle was built by the Knights of St. John between 1406 and 1522 on a rocky peninsula between two harbors. Originally an island in ancient times, it later became connected to the mainland, forming a peninsula. The castle, with its square layout measuring 180m x 185m, was constructed using stones from the Mausoleum, one of the Seven Wonders of the Ancient World, which was destroyed over time by earthquakes. Within the inner castle, there are French, Italian, English, German, and Spanish (Snake) towers. The tallest is the French Tower, reaching 47.50 meters above sea level. Aside from the eastern wall, other sections are reinforced with double defensive walls. Access to the inner castle requires passing through seven gates, each adorned with coats of arms depicting crosses, horizontal or vertical bands, and figures of dragons and lions. The inner castle also contains 14 cisterns, including the area under the chapel. Notable features include the keep, the double-wall moat, a drawbridge, a watchtower, and the inscription of Sultan Mahmud II. After the conquest of Rhodes by the Turks in 1522, the knights abandoned Bodrum and its surroundings on January 5, 1523. The castle served as a prison from 1895 but was partially destroyed when bombarded by French and British forces during World War I on May 26-28, 1915. Bodrum Castle is a remarkable historical monument with its multi-layered structure, combining ancient foundations, Gothic architectural elements from the 15th-century European Knights of Rhodes, and Ottoman-period additions. Now home to the Bodrum Museum of Underwater Archaeology, Bodrum Castle is also included in the UNESCO World Heritage Tentative List.

The Bodrum Underwater Archaeology Museum, located in Bodrum Castle, is a unique museum in Türkiye dedicated to underwater archaeology. It has been open since 1964 and showcases a diverse collection of underwater artifacts dating from the 16th century BCE to the 16th century CE, mostly discovered during underwater excavations off the coast of Türkiye. The museum features various halls dedicated to shipwrecks like the Uluburun Shipwreck and the Serçelimanı Glass Shipwreck, exhibiting significant finds and information on maritime history. Additionally, the museum displays land finds from the Bodrum Peninsula, shedding light on its history through exhibitions on necropolises and cultural artifacts. The museum also presents the history of underwater archaeology in Türkiye, highlighting the pioneering efforts of individuals who laid the foundations of this field. Various exhibition sections within the museum showcase a vast collection of amphorae, amphora production centers, and the evolution of underwater exploration techniques. Bodrum Castle, where the museum is located, was built by the Knights of St John in the 15th century and is considered a remarkable structure in the Eastern Mediterranean region.