Nostra Segnora de Mesumundu ("Our Lady of Mesumundu") is a religious building in the territory of Siligo, Sardinia, Italy. Located in the archaeological complex with the same name, it was built during the Byzantine domination of the island, over a pre-existing Roman structure.
The Byzantines re-used walls of the Roman baths, as well as the aqueduct. According to some sources, the edifice could have been used as a baptistery. However, it is also possible[1] that it was used for the purification of ill people through an immersion rite.
In the 10th century the structure was donated by the Giudice (duke) Barisone I of Torres to the Abbey of Montecassino. When monks came from the Italian religious community, they adapted the building for Roman Catholic use, adding an apse and a new entrance (demolished in 1934). For the work they used materials from the nearby Roman ruins and the nuraghe Culzu.