The Church of Nossa Senhora da Anunciação (Portuguese: Igreja Paroquial de Mértola/Igreja de Nossa Senhora da Assunção/Igreja de Nossa Senhora da Anunciação) is a 12th-century church and former mosque in the civil parish of Mértola in the municipality of Mértola, in the Portuguese Alentejo.

The building was likely built at the end of the 12th century as a mosque.

But, by the 13th century, the building had already become transformed into a Christian church, and its altar relocated to the northern wall. It was re-installed in the east sometime at the end of the 15th century.

In 1506, Duarte de Armas represented the church with a timber roof truss and a minaret/tower.

By the middle of the 16th century, though, Pedro Dias described the changes to the building: the minaret had already been substituted for a belltower and the roofline had become adorned with merlons, which crown the roof of the building (authored by Fernão Pires).

Between the 17th and 18th century, the belltower was redecorated.

On 2 February 1969, the region experienced an earthquake resulting in damage to buildings on the hilltop, including the church.

Source and more info: en.wikipedia.org/wiki/Church_of_Nossa_Senhora_da_Anunciação