Old San Juan

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 de 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.

Vieques Mosquito Bay

The Bioluminescent Bay (also known as Puerto Mosquito, Mosquito Bay, or "The Bio Bay"), is considered the best example of a bioluminescent bay in the United States and is listed as a national natural landmark. The luminescence in the bay is caused by micro-organisms, dinoflagellates, which glow whenever the water is disturbed, leaving a trail of neon blue.

A combination of factors creates the necessary conditions for bioluminescence: red mangrove trees surround the water (the organisms feed off the dead leaves); a complete lack of modern development around the bay; the water is cool enough and deep enough; and a small channel to the ocean keeps the dinoflagellates in the bay. This small channel was created artificially, being the result of attempts by the occupants of Spanish ships to choke off the bay from the ocean. The Spanish believed that the bioluminescence they encountered there while first exploring the area, was the work of the devil ('El Diablo') and tried to block ocean water from entering the bay by dropping huge boulders in the channel. The Spanish only succeeded in preserving and increasing the luminescence in the now isolated bay.

Kayaking is permitted in the bay and may be arranged through local vendors. Swimming is allowed on limited basis through guided tours.