A 12th-century collegiate church, begun under the Counts of Champagne and never completed — the nave was abandoned partway through construction when funds ran out, and a modest baroque facade was tacked on much later instead. The result is an odd, lopsided silhouette that puzzles visitors used to the symmetry of French Gothic cathedrals.
The choir and transept that do exist are early Gothic and fine examples of the style. The crossing is topped by an unusual octagonal dome added in the 17th century after the original collapsed. The bell tower behind it is older still, and its roof was rebuilt in the 1900s after a fire.
Inside, the church is light, austere and high-ceilinged. There are a few good 17th- and 18th-century paintings. Joan of Arc is said to have prayed here in 1429, on her way back from coronation at Reims.