In the 18th century, Portugal underwent a reorganization of its military. During this reorganization, three regiments were assigned to Olivenza: one cavalry regiment and two infantry regiments. For the regiment of cavalry, Dragons of Olivenza, barracks were built behind the Baluarte del Príncipe, which is still preserved today. To complement the cavalry barracks, the San Carlos barracks were built nearby to serve mainly as a warehouse for straw.
Until the 1970s, they served as a grain silo, but had fallen into disrepair. Since that decade, they were recovered by the City Council, much like the rest of the historical buildings. In fact, the castle, barracks and convents, which were in the possession of the Ministry of the Army, were used for social and cultural purposes.
The southern façade is notable for its enormous buttresses. The entire complex is characterised by its sober lines and neoclassical taste, where hardly any linteled windows can be seen.
Distributed in two levels, with large spaces, under a gabled roof. It has been partially restored in order to convert it into a Home for the Elderly. This rehabilitation earned it the important Europa Nostra award, which highlights the success of its restoration.