Biblioteca Carnegie

San Juan National Historic Site (Spanish: Sitio Histórico Nacional de San Juan) in the Old San Juan section of San Juan, Puerto Rico, is a National Park Service-managed historic site which protects and interprets colonial-era forts such as Castillo San Felipe del Morro, bastions, powder houses, and three fourths of the old city wall.

The San Juan City Wall (Spanish: Murallas del Viejo San Juan) is a city wall that surrounds the western end of the Islet of San Juan, site of the historic Old San Juan district in San Juan, Puerto Rico. This defensive wall system was built between the 16th and 20th centuries to protect the city and the Bay of San Juan, a highly strategic point in the Caribbean. These walls, along with the defensive fortresses in Old San Juan (La Fortaleza, El Morro and San Cristóbal), form part of the UNESCO World Heritage Site-designated San Juan National Historic Site as they are characteristic examples of the historic methods of construction used in military architecture which adapted European designs and techniques to the special conditions of the Caribbean port cities.San Juan remains the only walled city under the United States jurisdiction, with walled cities like Boston, Charleston and New Orleans no longer having walls after the 18th century, although St. Augustine, Florida still retains several wall remnants. Examples of other North American walled cities that retain their ramparts are Quebec City in Canada and Campeche in Mexico. The bartizans (garitas) found along the walls are considered emblematic of the city of San Juan and a symbol of historic heritage preservation in Puerto Rico.

The Antiguo Casino de Puerto Rico, located at Avenida Ponce de León 1 in San Juan, Puerto Rico, is a Beaux Arts architecture style building dating from 1917. It was listed on the National Register of Historic Places in 1977.

Castillo San Cristóbal is a fortress in San Juan, Puerto Rico. It was built by the Spanish to protect against land-based attacks on the city of San Juan. It is part of San Juan National Historic Site. Castillo San Cristóbal is the largest fortification built by the Spanish in the New World. When it was finished in 1783, it covered about 27 acres of land and partly encircled the city of San Juan. Entry to the city was sealed by San Cristóbal's double gates. After close to a hundred years of relative peace in the area, part of the fortification (about a third) was demolished in 1897 to help ease the flow of traffic in and out of the walled city. This fortress was built on a hill originally known as the Cerro de la Horca or the Cerro del Quemadero, changed to Cerro de San Cristóbal in celebration of the Spanish victories ejecting English and Dutch interlopers from the island of this name in the Lesser Antilles. At the time, it formed part of the insular territorial glacis of Puerto Rico. Castillo de San Cristóbal also contains five cisterns that were used for the storage of water during the ages of the Spanish Colony. They are extremely large (24 ft tall, 17 ft wide, and 57 ft long) and were used as bomb shelters during World War II.

Old San Juan (Spanish: Viejo San Juan) is a historic district located at the "northwest triangle" of the islet of San Juan. Its area roughly correlates to the Ballajá, Catedral, Marina, Mercado, San Cristóbal, and San Francisco sub-barrios (sub-districts) of barrio San Juan Antiguo in the municipality of San Juan, Puerto Rico. Old San Juan is the oldest settlement within Puerto Rico and the historic colonial district of the city of San Juan. This historic district is a National Historic Landmark District and is listed on the United States National Register of Historic Places as the Old San Juan Historic District. 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. Historically the mixed use commercial and residential real estate in the main streets like Cristo Street, Fortaleza Street (north) from Tanca Street to the Governor’s Mansion is the most valuable in the area and it has kept its value and increased steadily through several years despite the past economic turmoils.

San Juan Antiguo (not to be confused with the historic district of Old San Juan which is located within this district), is a barrio located in the municipality of San Juan in the Commonwealth of Puerto Rico. San Juan Antiguo has 7 subbarrios. In 2010, San Juan Antiguo had a population of 7,085 inhabitants and a population density of 2,681.9 people per km2. San Juan Antiguo is entirely located within the Isleta de San Juan, the islet off the coast of Puerto Rico where Old San Juan was settled, connected to the mainland by bridges and a causeway.

Casa de España is the headquarters of a private social organization whose members are those of Spanish descent in San Juan, Puerto Rico on Avenida de La Constitución in Old San Juan.

San Cristóbal, within Old San Juan, is one of the seven subbarrios of San Juan Antiguo barrio in the municipality of San Juan in Puerto Rico.

The Isleta de San Juan (Spanish for Islet of San Juan) is a 3-square-mile (7.8 km2) island in the San Juan Bay in the Atlantic coast of northern Puerto Rico. Home of 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 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 (El Capitolio).

The Senate of Puerto Rico (Spanish: Senado de Puerto Rico) is the upper house of the Legislative Assembly of Puerto Rico, the territorial legislature of Puerto Rico. The Senate, together with the House of Representatives of Puerto Rico, control the legislative branch of the government of Puerto Rico. The structure and responsibilities of the Senate are defined in Article III of the Constitution of Puerto Rico which vests all legislative power in the Legislative Assembly. Every bill must be passed by both, the Senate and the House, and signed by the Governor of Puerto Rico in order to become law.The Senate has exclusive power to try and to decide impeachments. The constitution also establishes that all secretaries appointed by the governor to the different executive departments, as well as all judges and the Comptroller, require the advice and consent of the Senate. Justices of the Supreme Court can not assume office until after confirmation by the Senate.The Senate has 27 members. Sixteen are elected from senatorial districts, with two senators per district, while an additional 11 which are elected at-large.The Senate has been meeting since 1917, after the enactment of the Jones–Shafroth Act established the body formally. The current session is the 27th Senate of Puerto Rico which has a majority from the Popular Democratic Party of Puerto Rico; giving the party control over the Senate without political opposition including constitutional amendments.The Senate, along with its members and staff, are housed in the eastern half of the Capitol of Puerto Rico. These buildings are usually the Rafael Martínez Nadal Senate Annex Building, the Luis Muñoz Marín Office Building, the Antonio R. Barceló Building, the Luis A. Ferré Building, the Ramón Mellado Parsons Office Building and the Baltasar Corrada del Rio Office Building.

Plaza Colón (Spanish for Columbus square or plaza), formerly called Santiago Square, is a plaza or public town square located in Old San Juan where the easternmost city walls and main city gate (Puerta de Santiago) used to be located. The square today is a popular meeting place and is often used as a starting point for sightseeing in Old San Juan as it is located close to the main cruise ship docks, numerous restaurants, cafés and gift shops, and important landmarks such as San Cristóbal Castle, Tapia Theater, the Old Casino and the Puerto Rico capitol.

The Capitol of Puerto Rico (Spanish: Capitolio de Puerto Rico) is located on the Islet of San Juan just outside the walls of Old San Juan. The building is home to the bicameral Legislative Assembly, composed of the House of Representatives and Senate. The building is located in the Puerta de Tierra sector of San Juan. The Capitol is also commonly referred to as the Palace of the Laws (Spanish: Palacio de las Leyes).