This castle was built during the Moorish occupation and some changes were ordered by the Portuguese kings since the Middle Ages. During the Restauration War, Spain tried to reconquest cities and towns near the border, besieging Portuguese fortresses. As the garrison of Juromenha Castle was short of elements, some students were mobilised and included in the garrison. On January 19th 1659 a doctor came to see a very sick man in the basement of the Governor house. Realising that the patient was about to die, he asked for a priest to offer the extreme unction to the patient. The students came with one after dark. Using a torch to find their way to the patient, they arrived with the priest, not aware that the place was a gunpowder magazine. A devastating explosion soon occurred, destroying a lot of buildings inside walls and causing over 200 deaths.
On the 21st century the walls and bulwarks have been restored, but not most buildings, still in ruins as the photo shows.