En 1777 uno de los aljibes se reventó, posiblemente durante las labores reconstructivas. Con el paso del tiempo y la instalación del agua corriente, estos espacios quedaron en abandono. En 1998, mientras se realizaban trabajos arqueológicos en la fortaleza, un grupo de investigadores descendieron en cuerdas al aljibe que se encuentra a un lado de la Casa del Gobernador, donde fueron hallados cantidades de documentos históricos olvidados desde la década de 1940.
Cisterns for storage of fresh water
One of the main aspects of any fortification is the water supply. Cisterns and wells were used to collect rainwater as means of storing the needed water for all the functions of the fort. These were one of the first features built on the fort, beginning shortly after its planning between 1689 and 1693. It was vital for the troop and the people that worked day by day on its construction to have a supply of drinking water.
During the reconstruction of the fort, between 1768 and 1775, the three existing cisterns were in a very poor state. Contractors, builders, architects and even the island Governor wrote letters mentioning the necessary repairs of the cisterns, more impending where its floors, walls, and vaults which had been damaged during the explosion in 1762. The cisterns were first inspected in 1768 and finally rebuilt by 1781. In 1777 one them burst, possibly during its reconstruction. Their rebuilt had a total cost of about 390 pesos.
With the later and more modern installation of running water on the fort, the cistern system became obsolete. In 1998, while conducting archaeological work in the fortress, archaeologists descended into the cistern located next to the Governor's House where they found many historical documents that were deposited there into the 1940's.