This church not only features some graceful architectural outlines and a rich mix of styles and history, but also a delicate and elegant set of sculptures that decorate the doors, apse and walls.

The former collegiate church of Santa María la Mayor, which was consecrated in 1155, is a Romanesque building of one nave in six sections, a presbytery and semi-circular apse, with pointed barrel-vaulted ceilings. Its magnificent doorway of three rounded archivolts features base reliefs and sculptures attributed to the French sculptor known as the Master of Oloron.
The tower was constructed in the 14th-15th centuries. It has small towers on its sides, a parapet with battlements and a 16th-century spire topped with pinnacles and finished in Gothic tracery.
Notable in the interior is the Gothic sculpture (13th century) of the church's patron and the Baroque main altar (1649), with panels by Jusepe Martínez. The sacristy (now taken down) was constructed in the 16th century, as was the beautiful adjoining cloister (1557), with its star-shaped cross vaults and eight Renaissance doors.