The Torre Blanca, or White Tower, like the Tower of Solsona, was one of the advanced fortifications for the castle of Castellciutat. The latter protected the defensive complex from the southern flank.
Originally its defences seem to have been limited to an artillery tower surrounded by polygonal fortifications for the infantry. In 1720, the greatest of the Bourbon military engineers, Alexandre de Retz, was in charge of reconstructing the defences. The tower was completely rebuilt and a powerful hornwork was built in front, which would later be used as the arsenal for the modern barracks, as well as complementary facilities that made the area almost as strong as the Castle.
The White Tower, along with the whole fortified complex, suffered the ravages of the war and the sieges of 1822 and 1875. In the 1950s, the Spanish army chose this site on which to build a large modern barracks that housed the Regiment de Caçadors de Muntanya Arapiles 62 (the 62nd Mountain Light Infantry Regiment ‘Arapiles’). Feeding the garrison had a major impact on the daily life of the people of La Seu d’Urgell. In 1993, the military installations were given over to the municipality of La Seu d’Urgell.