The water supply has always been one of the most serious problems for any type of fortification, especially since there is no source inside. The only solution was the cisterns. Water intended for human consumption was collected from the roofs of buildings. For other uses, such as watering horses or cooling cannons, the water was used, whenever possible, from the dams of roads or ditches.
Hostalric Castle has four cisterns. The only one that can be visited is located on the embankment of the covered road and stored rainwater from the ditch. It had exclusively underground access and its construction details indicate that it was built in the open air, that is, before the completion of the covered road. At present, the rainwater still keeps it full.