San Juan Islet is a 3-square-mile (7.8 km2) islet or small island on San Juan Bay in the Atlantic coast of northern Puerto Rico. Home to Old San Juan, it is the site of the oldest permanent European settlement in Puerto Rico (1521), and the second oldest European settlement in the West Indies after Santo Domingo (1496). Due to its strategic location in the Caribbean during the Spanish colonization of the Americas, it is home to a city wall and a number of militaristic buildings such as El Morro Castle. Today, it is also home to many of Puerto Rico's government buildings such as the territory's capitol building.