It was consecrated in 893 by seven bishops, as stated on the tombstone that is still preserved in the south side chapel.
It has a basilica layout with three naves, a triple apse with small chapels, and two compartments adjoining the north and south walls that form the pseudo-transept on the outside.
At the west end of the church there are three compartments corresponding to those of the east end. Above the central compartment stands the royal gallery that directly receives the light from a mullioned window in the main façade.
The tall, narrow naves are separated by semi-circular arches on square pillars lacking any decoration, while the apse chapels are separated from the naves by semi-circular arches that rest on columns with capitals decorated with plant motifs.
All the interior spaces are vaulted and conserve important remains of murals.
