The church, started in 1174, was finished around 1225. It was consecrated in 1211. It has a Latin cross plan, with a nave and lower aisles of six bays. The arms of the transept, which are the same width as the nave, each end in an apsidal chapel which is barely visible from the exterior. The chancel is rectangular, ending in the presbytery. The crossing is surmounted by a dome raised on a tall octagonal drum in Gothic style, and topped by a Baroque lantern.