San Juan, Puerto Rico in the context of "Guaynabo, Puerto Rico"

The barrios of Puerto Rico are the third-level administrative divisions defined with geographic boundaries serving as the primary legal subdivisions of the 78 municipalities in the archipelago and island of Puerto Rico, an unincorporated territory of the U.S. Amounting to 902 wards or boroughs equivalent to minor civil divisions in the U.S., like cities, townships, and parishes, barrios are under the governmental authority of the popularly elected strong mayor and unicameral legislature governing the municipality within which they are located. Barrios are subdivided into numerous subbarrios, districts, communities, and/or sectors.

Except for San Juan, Ponce, Florida, and Vieques, all municipalities have a barrio equivalent to a downtown area in the U.S. called pueblo, officially known as barrio-pueblo (literally "neighborhood-town"), which typically is the site of the historic Spanish colonial settlement, administrative center, and urban core of the municipality. Of the 902 barrios proper, 828 are barrios and 74 barrios-pueblos.

Puerto Rico (abbreviated PR), officially the Commonwealth of Puerto Rico, is a self-governing Caribbean archipelago and island organized as an unincorporated territory of the United States under the designation of commonwealth. Located about 1,000 miles (1,600 km) southeast of Miami, Florida, between the Dominican Republic in the Greater Antilles and the U.S. Virgin Islands in the Lesser Antilles, it consists of the eponymous main island and numerous smaller islands, including Vieques, Culebra, and Mona. With approximately 3.2 million residents, it is divided into 78 municipalities, of which the most populous is the capital municipality of San Juan, followed by those within the San Juan metropolitan area. Spanish and English are the official languages of the government, though Spanish predominates.

Puerto Rico was settled by a succession of Amerindian peoples beginning 2,000 to 4,000 years ago; these included the Ortoiroid, Saladoid, and Taíno. It was claimed by Spain following the arrival of Christopher Columbus in 1493 and subsequently colonized by Juan Ponce de León in 1508. Puerto Rico was contested by other European powers into the 18th century but remained a Spanish possession for the next 400 years. The decline of the Indigenous population, followed by an influx of Spanish settlers, primarily from the Canary Islands and Andalusia, and African slaves vastly changed the cultural and demographic landscape of the archipelago. Within the Spanish Empire, Puerto Rico played a secondary but strategically significant role compared to larger and wealthier colonies like Peru and New Spain. By the late 19th century, a distinct Puerto Rican identity began to emerge, centered on a fusion of European, African, and Indigenous elements. In 1898, following the Spanish–American War, Puerto Rico was acquired by the United States.

Ponce (US: /ˈpɔːnseɪ, ˈpoʊn-/ PAWN-say, POHN-, UK: /ˈpɒn-/ PON-, Spanish: [ˈponse] ) is a city and a municipality on the southern coast of Puerto Rico. The most populated city outside the San Juan metropolitan area, Ponce was founded on August 12, 1692 and is named after Juan Ponce de León y Loayza, the great-grandson of Spanish conquistador Juan Ponce de León. Ponce is often referred to as La Perla del Sur (The Pearl of the South), La Ciudad Señorial (The Manorial City), and La Ciudad de las Quenepas (Genip City).

The city serves as the governmental seat of the autonomous municipality as well as the regional hub for various government of Puerto Rico entities, such as the Supreme Court of Puerto Rico. It is also the regional center for various U.S. federal government agencies. Ponce is a principal city of both the Ponce Metropolitan Statistical Area and the Ponce-Yauco-Coamo Combined Statistical Area with, as of the 2020 US Census, a population of 278,477 and 333,426 respectively.

The San Juan–Bayamón–Caguas metropolitan area, most commonly known as the San Juan metropolitan area (Spanish: área metropolitana de San Juan), is the largest and most populous metropolitan statistical area (MSA) in Puerto Rico, concentrated in the capital municipality of San Juan and surrounding municipalities, including Bayamón, Caguas, and Carolina, on the northeastern coastal plain of the main island. One of 6 metropolitan statistical areas in Puerto Rico, it is within the San Juan–Bayamón combined statistical area (CSA), which is one of 3 primary statistical areas in the archipelago as defined by the United States Census Bureau. As of 2023, the estimated population of the San Juan–Bayamón–Caguas metropolitan area is 842,535 in municipalities in the conurbation and 1,193,198 in municipalities outside the urban core, making it the fourth largest in the insular Caribbean.

La Santa María de la Inmaculada Concepción (Spanish: [la ˈsãn̪.t̪a maˈɾi.a ð̞e̞ la ĩm.ma.kuˈla.ð̞a kõn̟.θeβ̞ˈθjõn] lit. 'The Holy Mary of the Immaculate Conception'), or La Santa María (Spanish: [la ˈsãn̪.t̪a maˈɾi.a]), originally La Gallega (Spanish: [la ɡaˈʝe.ɣ̞a]), was the largest of the three small ships used by Christopher Columbus in his first expedition across the Atlantic Ocean in 1492, with the backing of the Spanish monarchs. Her master and owner was Juan de la Cosa.

In 1492 the ship ran aground on a sand bar near modern day Cap-Haïtien of the island of Hispaniola. The wood of the ship was stripped and used to make a wooden fort at Limonade, and one anchor survives to the present day in a Museum in Haiti. In the 19th and 20th century several replicas have been made of varying nature, as the size and details of the original are unknown.

Old San Juan (Spanish: Viejo San Juan) is a historic district or quarter located at the "northwest triangle" of the islet of San Juan in 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 Puerto Rico Registered Historic Zone and a National Historic Landmark District, Old San Juan Historic District, and is also listed on the United States National Register of Historic Places. 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 Walls of Old San Juan (Spanish: Murallas del Viejo San Juan) is a defensive city wall that surrounds the western end of the San Juan Islet, site of the historic district of San Juan, Puerto Rico. This defensive wall system was built between the 16th and 18th 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.

Castillo San Felipe del Morro (English: Promontory Castle of Saint Philip), most commonly known as El Morro (The Promontory), is a large fortress and citadel in the Old San Juan historic quarter of San Juan, the capital municipality of Puerto Rico. Commissioned by King Charles I of Spain in 1539, it was first built as a fortified tower in honor of King Philip II, who oversaw its expansion into a hornwork bastion fort by 1595. Over the next 200 years, especially in the reign of King Charles III, El Morro continued to be developed to reach its current form in 1787. Rising 43 metres (140 ft) from the Atlantic shoreline with 5.5 to 7.6 metres (18 to 25 ft) thick walls, the six-leveled edifice stands on a steep, rocky headland promontory on San Juan Islet guarding the entry to San Juan Bay, the harbor of Old San Juan. El Morro, alongside La Fortaleza, San Cristóbal, El Cañuelo, and other forts part of the Walls of Old San Juan, protected strategically and militarily important Puerto Rico, or La Llave de las Indias (The Key to the Indies), from invasion by competing world powers during the Age of Discovery and Sail. It was designated a World Heritage Site by UNESCO in 1983.