Bodrum Castle, also known as the Castle of St. Peter, is a historic fortress located in the port city of Bodrum in Turkey, on the southern coast of the Bodrum Peninsula, at the entry into the Gulf of Gökova. Built by the Knights Hospitaller starting in 1402, it was constructed on the site of the ancient city Halicarnassus, primarily for the purpose of defense against the Seljuk Turks. Over the centuries, the castle has served as a military garrison and a prison. Today, it stands as a prominent museum, particularly the Museum of Underwater Archaeology. Within its walls, visitors can admire various artifacts from shipwrecks and ancient maritime history. The castle's towers offer panoramic views of the city and the Aegean Sea. Its architecture is a fusion of styles that reflect the castle's diverse history and the array of cultures that have occupied it over time, including Ottoman and Mediterranean influences.