[3] Several historical buildings and structures, particularly La Fortaleza, the city walls, and El Morro and San Cristóbal castles, have been inscribed in the UNESCO World Heritage Site list since 1983.

The city is characterized by its narrow, blue cobblestone streets, and flat-roofed brick and stone buildings, which date back to the 16th and 17th centuries—when Puerto Rico was a Spanish possession.

Near Fort San Felipe del Morro, is the Casa Blanca, a palace built on land which belonged to the family of Ponce de León.

The ruins of Caparra are known as the Pueblo Viejo sector of Guaynabo, behind the almost land-locked harbor just to the west of the present San Juan metropolitan area.

[11] Also constructed in 1521, Casa Blanca served as the first fortification of the settlement and residence of Juan Ponce de León and his descendants until the mid-eighteenth century.

Some of these include the Thomas Aquinas Convent (today the National Gallery of Puerto Rico) in 1523, Nuestra Señora de la Concepción Hospital in 1524, and the former Gothic stone cathedral building.

[12] The strategic position of Old San Juan in the context of the Caribbean and the Atlantic Ocean also made it a target for foreign attacks, which motivated the erection of a city wall between 1530 and 1560.

He followed the example suggested by his father, a local civic leader who had successfully prevented the demolition of the Capilla del Cristo in favor of a traffic redesign.

He advised mayor Rincón de Gautier in having local zoning laws changed to favor remodeling and the incorporation of Spanish colonial motifs in any new construction.

[citation needed] Luis Muñoz Marín, as a senator and later as governor of Puerto Rico, supported and implemented what became known as Operation Bootstrap, which included the development of the tourism industry.

[19] These efforts were further supported by the 1955 creation of the Institute of Puerto Rican Culture (Instituto de Cultura Puertorriqueña) head by Alegría.

At the time, most real estate in Old San Juan had devalued under appraised values because the city was perceived as unsafe (particularly because of building disrepair and social ills such as prostitution) and not profitable for business (because of rent control statutes, as well as the reluctance of commercial banks to fund remodeling).

As in other Operation Bootstrap projects, the Woolworth family was invited in 1957 to reconstruct the former convent (which had more recently been a low-rent apartment building and city garage) into the luxury Hotel El Convento.

[23] La Perla (Spanish for the pearl) is a former shanty town or informal settlement located along the northern section of the historic San Juan city walls.

[25] With its abundance of shops, historic places, museums,[26] open air cafés, restaurants, colorful homes, tree-shaded plazas, and its old beauty and architectural peculiarity, Old San Juan is a main spot for domestic and international tourism.

The district is characterized by numerous public plazas, which are filled with local shops that sell traditional craftwork,[27][28] sculptures and typical musical instruments.