The fine campanile of the church is 246 ft.
On the south side of the façade is a large brick campanile, and the foundations of another may be seen on the north.
Sofia, a circular edifice of about 760, now modernized, the roof of which is supported by six ancient columns, is a relic of the Lombard period; it has a fine cloister of the 12th century constructed in part of fragments of earlier buildings; while the cathedral with its fine arcaded facade and incomplete square campanile (begun in 1279) dates from the 9th century and was rebuilt in 1114.
In the central square stands one of the finest belfries of northern France, a square structure surmounted by a wooden campanile, dating from the 14th century.
Ursus in 370-390, which had a nave and four aisles, was destroyed in 1734-44, only the (inaccessible) crypt and the round campanile remaining from the earlier structure; there are fragments of reliefs from a pulpit erected by Archbishop Agnellus (556-569) in the interior.