Located down from the Castle, next to Porta D. Manuel I, the church built between 1541 and 1551 is considered the most remarkable Renaissance expression of the Algarve. It is the work of the master mason André Pilarte, then resident in Tavira, who worked on the construction of the Jerónimos Monastery in Lisbon. The Renaissance characteristics are well evident in the composition and decoration of the main portico, in perfect back arch, decorated with motifs inspired by Italian engraved, finished by an admirable sculptural set that integrates the image of Our Lady of Mercy, in the center, flanked by the figures of St. Peter and St. Paul and the weapons of the kingdom and the city. This building uses a typology of three naves and four formed by framed arches on columns with carefully ornamented Renaissance capitals. In place of the previous 16th century altarpiece, painted by Pedro da Campania, we find from the Baroque period three magnificent altarpieces: the chancel and two collaterals, dating from 1722. The main altarpiece is by the master tavirense carvers Manuel Abreu do Ó. In 1754 four baroque windows were opened in the body of the church by the distinguished master Diogo Tavares de Ataíde, and in 1760 18 panels of blue and white figurative tiles were placed, executed in the workshop of a Lisbon master. They represent the 14 spiritual and bodily works that guide the activity of the brotherhood of Mercy and some Steps of the Life of Christ. They constitute an interesting manifestation of the Rococo form, with some excerpts missing today.