[6][7] The bay is a semi-enclosed body of water with an elaborate system of loops, basins and channels at the center of Puerto Rico's most significant historical monuments and largest communities.

San Juan Bay provides recreation, sightseeing and tourist attractions, and its curved shape offers a variety of docking facilities for watercraft.

This impression comes from a neck of land, Puntilla ("small point"), which projects from the Islet of San Juan Bautista into the center of the bay and approaches another protuberance (Punta Cataño) stretching from the other side of a larger island.

Juan Ponce de León spent days searching for the best place to build a villa, the blueprint for a colonial city.

Santo Domingo governor Nicolás de Ovando had appointed him to pacify and evangelize the nearby island, which Christopher Columbus had named "San Juan Bautista" during his second voyage to the Americas.

[16] In 1508 Ponce de León sailed into the Bay of Guanica, on the west of the island, where local cacique Agüeybaná I welcomed his men as allies against the Caribs.

[18][19] Ponce de León pushed inland and ordered the first Spanish settlement on the island, 3 miles (4.8 km) from the bay.

Mendicant friars appealed to Ponce de León to move the settlement closer to the bay (and its sea breezes), saying that its present location was lethal to children.

According to Rodrigo de Figueroa's map, the villagers resettled on a 3-mile (4.8 km) blustery, wooded islet at the bay's entrance.

[34] By the eighteenth century the population of the islet had expanded into the Atlantic City of San Juan, largely due to the proximity of the bay and its port.

On the east side of the bay's mouth, the Castillo San Felipe del Morro still guards its narrow entrance.