The Old Tower of Oviedo was likely constructed in the late ninth century, as it shares similarities in construction to the holy chamber from that period. The tower has two distinct parts - the older, irregularly shaped bottom section with small windows, and the upper bell tower section with eight larger windows and arched columns. While its exact origins are undocumented, it is believed the primary purpose of the tower was to protect religious relics stored in the attached holy chamber from threats such as Norman or Muslim incursions.