The fortress above the lagoon was built to protect citizens from raids by pirates and the local indigenous population. It also served as an important outpost for the Spanish in the War of the Castes. In 1859 it was seized by Maya rebels, who held the fort until Quintana Roo was finally conquered by Mexican troops in 1901.
Today, with formidable cannons still on its ramparts, the fortress remains an imposing sight. It houses a museum exhibiting colonial armaments and uniforms from the 17th and 18th centuries.