Philip II, King of Spain, ordered in 1595 the construction of the Holy Mercy Chapel next to the entrance to the Fortress. However, in 1656 the chapel was re-built in the Old part of the town, where it stands today. Rectangular-shaped and austere-looking, its value lies on the inside: a Baroque altarpiece with an image of Jesus Christ in the cross. The cross was sent from México full of gold coins on the inside in times when gold trading was forbidden. It was a present from local emigrants living in America who wanted to finance the temple re-construction. Inside the chapel several images are kept: Jesus Christ with the lamps, the Dolorous Madonna, St. Isabel or the Immaculate Conception Madonna.

The heritage of temple belongs to the Santa Casa de Paz y Misericordia (the Holy Mercy and Peace) Brotherhood, established in 1574 to honour St. Isabel. The brotherhood, which is the most ancient in Galicia, was created to fulfil the merciful principles of the Catholic religion, basically to give Christian burial and a proper funeral to local people and foreigners who die in the town. The Brotherhood is in charge of the Holy Week ceremonies in the village since its establishment.