Fort Jefferson is a large coastal fortress located in the Dry Tortugas, a group of islands off the coast of Florida. Built between 1846 and 1875, it was designed to protect the shipping lanes of the Gulf of Mexico and the entrance to Key West. The fort is made of brick and features a unique star-shaped design, which was common in military architecture of that era. Today, Fort Jefferson is part of Dry Tortugas National Park, attracting visitors for its historical significance and natural beauty. The fort is accessible only by boat or seaplane, making it a remote destination for those interested in exploring its history and the surrounding marine environment.