The Lourinhã parish church, an example of 14th-century architecture, honours St Mary and has been a national monument since June 1910. Known as Castelo Church – it is believed that the earliest construction stands within the walls of an old castle which has disappeared over time - it was erected early in the 12th century by Lord Jordan de Lorient, a French crusader to whom King Afonso Henriques donated the lands of Lourinhã as a reward for his services, rendered in the conquest of Lisbon from the Moors.

During the reign of King João I (1384-1397) the temple was rebuilt, enlarged and consecrated by Lord Lourenço Vicente, the Archbishop of Braga, supporter and close advisor to the Master of Avis during the 1383/1385 crisis, and also the author of the acclamation speech delivered by the Master of Avis, King of Portugal, at the Courts of Coimbra in 1385.

It is a Gothic monument, consisting of a central nave, two side aisles and a polygonal apse. The central nave, which is high and wide, is separated from the side aisles by eight ogival arches of great elegance, supported by three-metre-tall monolithic limestone columns, finished off with elegant capitals, all different, worked and embellished with plant motifs.

In the chancel, with its octagonal shape and a dome held by thick bevelled ribs, armoured shields are visible. On the wall, the Manueline niche, framed by sculpted ropes, which was used to keep the holy oils, was later converted into a tabernacle. You can also admire the various mason's marks engraved on the stone walls. The baptismal font is octagon-shaped and has two crosses in a circle and a five-pointed star, which are symbols associated with the passage, or stay, of the Templars in this region.

Outside, the main portico faces the sea and is topped by a beautiful rose window, typical of that era. It has four archivolts with capitals which tell stories through their scenes of rural family life and the Old Testament. The ogival door on the north side, with bevelled edges and decorated with sculpted masks and scallop shells, places Lourinhã on the pilgrimage routes to Santiago de Compostela. To the south, you can see the corner of the building resting on a Roman stone.

From the Castle’s Belvedere, a level above the church and marking the probable spot where the old castle had stood, you can admire the Crossing and its beautiful 16th-century capital, and view the vast landscape that extends down to the sea.