The architecture of San Juan is very diverse, due to its size and all the cultural influences received during its existence. The oldest part of the city, known as Old San Juan, mostly features the influence of Spanish architecture. This part of the city is comprised by a network of "setted" roads usually surrounded by ancient, two-storied houses built on masonry. Some colonial structures have been restored and serve either as government offices or museums. Some examples are the Ballajá Barracks, which now serve as museum and headquarters of several cultural organizations; La Fortaleza, which has served as the residence of the Governor of Puerto Rico since the 16th Century; and the Ancient Welfare Asylum, which now houses the Institute of Puerto Rican Culture, among others. Old San Juan also features several public squares, like the Plaza de Armas, located in front of San Juan City Hall; and cathedrals, like the Cathedral of San Juan Bautista. Old San Juan is also notable for being partly enclosed by massive walls and fortifications built by the Spanish government.