La Fortaleza (lit., "The Fortress" ) is the official residence of the governor of Puerto Rico. It was built between 1533 and 1540 to defend the harbor of San Juan. The structure is also known as Palacio de Santa Catalina (Saint Catherine's Palace). It is the oldest executive mansion in continuous use in the New World. It was listed by UNESCO in 1983 as part of the World Heritage Site "La Fortaleza and San Juan National Historic Site".