This chapel dedicated to Our Lady of A Lanzada was part of a 10th-century fortress, along with a late Roman necropolis and a medieval tower. The tower was part of a defensive system along with the towers of Cambados (Torre de San Sadurniño) and Catoira (Torres del Oeste). The chapel was built in the Romanesque style in the early 13th century. It is composed of a single nave and a semicircular apse with roofs at different heights.
Outside, the doorway on the facade is topped by a tympanum and a trefoil-shaped rose window, and the south side has another semicircular door and a small window. The north and the east sides are decorated with more small windows. The semicircular apse has four buttress-like columns and open windows, which are the most recent. The Roman tile roof is adorned with three stone crosses of different styles and shapes.
The interior is divided into the nave and an apse with the statue of Saint Mary, patron of fertility, who is honoured every year on the last Sunday of August. One of the oldest fertility rituals in Galicia, based on the powers of water and the influence of the moon, has long taken place in this chapel