This is the oldest monument in the town: the building was already there in the year 1000. The high front extension in front of it dates from the same era. The nave and the very attractive apse are from the 12C. The interior is partly topped by a gallery thus forming two rows of superposed columns. Its capitals are richly decorated. The church has two Romanesque crypts. The treasure house has precious reliquaries, ivories and liturgical ornaments.