This fort stands guard at where once was the eastern gate to the walled city of Old San Juan. Construction on the fort was begun in 1634 and finished in 1790, although modifications were made well into the 18th Century. Its better-known sister fort, 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, this fort 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 fort built by the Spanish in the New World. Guided tours will show you 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.