Due to San Juan’s vulnerability from land attacks, Spanish officials ordered the construction of defence works to the east of the city. Starting in 1634 with a small, triangular-shaped fortification on San Cristóbal hill, the construction of Castillo San Cristóbal took nearly 150 years to complete. By the time of its completion San Cristóbal and El Morro formed the cornerstones of the largest fortification system in Spanish America.
San Cristóbal was designed to provide a ‘defence in depth’. Not only did the complex system include a main structure, it also had an elaborate network of batteries, walls and moats. Each layer of defence supported another layer. The outer defences, like those of El Morro, included a large, open field or esplanade, that attackers would have to cross while facing a punishing fire from defenders.
Today, features from the 1760s through to the 1960s can still be seen. Large, concrete blocks scattered on the lawn were left by the U.S. Army, which was stationed in the castle from 1898 to 1960. The grass-roofed building that now houses the park visitor facilities was built by the Americans in 1942 as a World War II command post. Other features were built by Spanish, mostly in the late 1700s.
The large rooms at the entrance to Castillo San Cristóbal, which are found in most Spanish fortifications, are called casemates and were built in the late 1700s. They were designed with gun ports for cannon and were bombproof. These vaults housed almost all aspects of military life, including quarters for troops, a kitchen and a latrine. The arch in the ceiling provided strength to support gun decks above and to withstand the concussion of shells exploding overhead.
Within Castillo San Cristóbal are five huge cisterns each 17 metres long, 7 metres high and 5 metres wide (57 feet long, 24 high and 17 feet wide). The cisterns can be accessed by wells, enclosed in masonry cylinders. Combined, the cisterns can hold about 870,000 gallons of water and every floor and roof in the fortification was designed to catch rain water and drain it into the tanks.
Beneath the fortress are six hidden passages. The tunnels, sometimes called galleries, were an important part of fortifications like San Cristóbal. They protected soldiers from enemy fire and enabled commanders to move large numbers of troops to new positions, unseen by the enemy.
The tunnel that leads from the main plaza is the longest of the fortress’ underground passages and was built around 1769. The opening was originally a gunport or embrasure aimed at the castle’s moat. Around 1942 the U.S. Army converted the opening into the doorway that can be seen today.
Grooves remain along walls of the tunnel, where it could be countermined with explosives if an enemy entered. About half way along the tunnel is a small dungeon where a Spanish captain was held, awaiting execution for mutiny. On the walls of the dungeon the captain drew pictured of galleons, which can still be seen today.
Garitas, or sentry boxes, protruded from high vantage points in order to watch for landward and seaward approaches. The garitas were built to accommodate one man and had low doorways and ceilings, reflecting the short stature of soldiers at that time. Twenty-eight such garitas remain on the fortresses and city walls of Old San Juan and today Puerto Rico honours the garita as a symbol of the island’s heritage.
The Garita del Diablo, in San Cristóbal, is the oldest in San Juan, built between 1634 and 1635, and was given its name of Devil’s Sentry Box as it was believed to be haunted. The narrow openings protected the sentry from enemy fire, focused the soldier’s vision and discouraged distractions.
Soldiers stationed on duty in the sentry boxes would spend long days and dark nights alone, scanning the horizon. Stories tell of soldiers seeing apparitions of beautiful women who seduced them and caused their desertion or disappearance. Centuries of ocean spray, rain and wind badly damaged the Garita del Diablo and, in 2004, workers carefully restored it.
From the mirador in San Cristóbal, visitors can see many of San Juan’s special features including the San Juan Harbour, the Capitol Building of Puerto Rico, the Tapia Theatre and the Bacardi Rum Distillery.
The view today is quite different from the one that soldiers stationed in the fortress centuries ago would have seen. At that time the shore came up to the base of Castillo de San Cristóbal and the city walls. When a large part of the city wall was demolished in the late 1800s, the rubble was used to create more land. As a result the shoreline is now around 400 metres (almost one quarter of a mile) from San Cristóbal and buildings now fill the area that once was the harbour.
- Information signs at Castillo San Cristóbal