Old San Juan is located on a small and narrow island which lies in the north coast, about 35 miles (56 km) from the east end of Puerto Rico, and is united to the mainland of Puerto Rico by the three bridges. It is bounded by the Atlantic Ocean to the north and to the south by San Juan Bay or "Bahia of San Juan" which lies between the city and the mainland. On a bluff about 100 feet (30 m) high at the west end of the island and commanding the entrance to the harbor rise the battlements of Fort San Felipe del Morro, in which there is a lighthouse.
The "Caño de San Antonio" lies also in South Coast and extends to the Southeast where the island of Old San Juan connects to the mainland through Santurce by three bridges, "Puente Dos Hermanos" (Ave. Ashford), "Puente G. Esteves" (Ave. Ponce de León) and "Puente San Antonio" (Ave. Fernández Juncos).
The city is characterized by its narrow, blue cobblestone streets and flat-roofed brick and stone buildings dating back to the 16th and 17th century when Puerto Rico was a Spanish possession. Near Fort San Felipe del Morro is the Casa Blanca, a palace on land which belonged to the family of Ponce de Leon.