The devastating effects of the attacks by the English in 1598 and the Dutch in 1625 forced the Spaniards to expand the fortification system of San Juan. They lengthened the city walls and constructed a sentry box or “garita” (Garita del Diablo) on the coast to the east of El Morro and also a small artillery platform on top of a hill named San Cristóbal. . . . Following the principles of the French-influenced “Vauban-style fortress” (featuring irregular and triangular shaped bastions) and a “Defense in Depth” strategy, San Cristóbal was built with a deep dry moat and a series of tunnels. These tunnels protected soldiers from enemy fire and allowed the safe movement of troops, weapons and supplies. This enabled the defenders to engage the enemy before they reached the city gate if attacked by land. Gunpowder could be placed in other tunnels, called “countermines” to explode beneath the feet of an attacking enemy. Countermining tunnels served to destroy parts of the battlefield and also had the potential to block enemy access to the fortress through them.
The main plaza of San Cristóbal was the heart of the fort. It is where troops drilled, were inspected and assembled for formal events. Eleven casemates border the plaza. Casemates are large vaulted, bombproof rooms designed with gun ports for cannon. The arch in the ceiling provided strength to support gun desks above and withstand the concussion of shells exploding overhead. Casemates also housed officers’ quarters, barracks, storage areas, the kitchen and latrine. Thick-walled gunpowder magazines were built close by the plaza, casemates and tunnels and were designed to provide optimal conditions for the storage of the powder. Artillery ramps provided access to the main firing battery and the dry moat.
National Park Service
Castillo San Cristóbal is a fortress in San Juan, Puerto Rico. It was built by the Spanish to protect against land-based attacks on the city of San Juan. It is part of San Juan National Historic Site. Castillo San Cristóbal is the largest fortification built by the Spanish in the New World. When it was finished in 1783, it covered about 27 acres of land and partly encircled the city of San Juan. Entry to the city was sealed by San Cristóbal’s double gates. After close to a hundred years of relative peace in the area, part of the fortification (about a third) was demolished in 1897 to help ease the flow of traffic in and out of the walled city.
This fortress was built on a hill originally known as the Cerro de la Horca or the Cerro del Quemadero, changed to Cerro de San Cristóbal in celebration of the Spanish victories ejecting English and Dutch interlopers from the island of this name in the Lesser Antilles. At the time, it formed part of the insular territorial glacis of Puerto Rico. Castillo de San Cristóbal also contains five cisterns that were used for the storage of water during the ages of the Spanish Colony. They are extremely large (24 ft tall, 17 ft wide and 57 ft long) and were used as bomb shelters during World War II.
As you enter the fort, the first thing on your left will be the guardhouse. In colonial times, the guards at this post would control access to the fort and enforce military discipline. Today, they’ll charge you a $3 entrance fee and hand out information about the fort and other nearby attractions. They’re also a lot friendlier! Immediately after the guardhouse you’ll see the main plaza, were Spanish soldiers conducted drills and punished the unruly. But before you walk towards the plaza, take a few steps back and walk up the ramp immediately to the left of the main entrance. This ramp leads to the North Battery, which was added by the Spaniards in 1897 to defend the north side of the fort from sea attacks. Ordoñez canons at this battery, similar to the one you see today, fired the first shots of the Spanish-American War on the morning of May 12th, 1898.
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Once you go to the first floor, you’ll be in the beautiful main courtyard of the fort. This courtyard was where military drills were held. The covered passageway to the left as you enter has a beautiful Instagram spot with richly colored textured walls and an old wagon. Along the periphery of the main courtyard are several rooms featuring ports for cannon. With thick bombproof walls, the rooms bring home the fact that you are in a formidably strong fortress. They housed living quarters, kitchen, and storage areas. Here also you will find the modest chapel.
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