is the capital and most populous municipality in the Commonwealth of Puerto Rico, an unincorporated territory of the United States. As of the 2010 census, it is the 46th-largest city under the jurisdiction of the United States, with a population of 395,326. San Juan was founded by Spanish colonists in 1521, who called it Ciudad de Puerto Rico
. Puerto Rico's capital is the third oldest European-established capital city in the Americas, after Santo Domingo, in the Dominican Republic, founded in 1496 and Panama City, in Panama, founded in 1519. Several historical buildings are located in San Juan; among the most notable are the city's former defensive forts, Fort San Felipe del Morro and Fort San Cristóbal, and La Fortaleza, the oldest executive mansion in continuous use in the Americas.