El Morro, officially known as Castillo San Felipe del Morro, sits atop a high promontory overlooking the entrance to San Juan Bay. It is the result of the efforts of many different Spanish engineers over a period of more than 250 years and is one of the largest forts built by the Spaniards in the Caribbean. Although the foundations were laid in 1539, the six-level fort was not considered completed until 1787. During World War II, the U.S. government added an annex of its own design on top of the fort. This massive structure suffered countless attacks from the likes of Sir Francis Drake in 1595 and the Dutch fleet in 1625. In 1898 American ships fired on it during the Spanish-American War, destroying its lighthouse, which was later restored. Visit casemates and stairways, aim your camera on the cannons that still guard the harbor, and gaze over the 60-foot tall walls at the ocean. Stroll on the lawns where soldiers once marched and watch the children flying their kites in the afternoon sea breezes. The fort can be explored everyday from 9:00 am to 6:00 pm either on your own or on one of the ranger led programs that will take you through the fortification and out onto the picturesque garitas, sentry boxes.

Castillo San Cristóbal stands guard at where once was the eastern gate to the walled city of Old San Juan. Construction on San Cristobal was begun in 1634 and finished in 1790, although modifications were made well into the 18th Century. Its better-known sister fortification, El Morro, was designed to protect the city from attacks by sea; San Cristóbal guarded from approaches by land. If you are interested in history, enjoy a walk on the ramparts, where half a millennium ago Spanish soldiers held their watch. If you love to photograph spectacular views, San Cristobal is a goldmine for you, with its panoramic view of the coast from Old San Juan to Condado and beyond. Wear comfortable shoes! Covering 27 acres, this is the largest fortification built by the Spanish in the New World.  See where the first shots of the Spanish-American War were fired and will reveal part of its intricate defense system, designed by two Irishmen in the employ of the Spanish crown. Don't miss the "Garita del Diablo", a sentry box that, according to one legend, devoured soldiers sent there on guard. A labyrinth of tunnels crisscrosses deep under ground where the dungeons are located, and the outside walls fall 150 feet straight onto the rocks of the north shore. Castillo San Cristobal is open to the public daily from 9:00 am to 6:00 pm.