The Chapel of Our Lady of the Agony stands west of the centre, close to the waterfront, and is one of Viana do Castelo's most important devotional sites. The present church grew out of an older chapel and was blessed in the 18th century; its detached rear tower, added in 1868, leaves space for pilgrims to circle the building during the annual rituals.
Its real importance is inseparable from the Romaria de Nossa Senhora da Agonia, the August pilgrimage that fills Viana with processions, traditional Minho dress, flower carpets, river parades, and the clattering pageantry of giants and big-headed figures. Visit quietly outside festival time for the church itself, or come in August if you want to see how deeply the shrine is woven into the city's identity.