The origins of this church stretch back over a millennium. First established by King Childebert in 543, who constructed a basilica and monastery on the site, it was built, destroyed, and rebuilt several times over the centuries. Nothing remains of the original buildings, but the bell tower dates from the 10th century and is one of the oldest in France. The church and its abbey became a major center of learning and power during the Middle Ages, remaining a force to be reckoned with up until the French Revolution, when all hell broke loose: The abbey was destroyed, the famous library burned, and the church vandalized. Restored in the 19th century, the buildings have regained some of their former glory, though the complex is a fraction of its original size.

Much of the interior is painted in a range of greens, and golds—one of the few Parisian churches to retain a sense of its original decor. The paint, however, is in a sorry state; the interior is scheduled to be restored during 2015. The heart of King Jean Casimir of Poland is buried here, as are the ashes of the body of René Descartes (his skull is in the collections of the Musée de l’Homme). On the left as you exit you can peek inside the chapel of St-Symphorien, where during the Revolution over 100 clergymen were imprisoned before being executed on the square in front of the church. The chapel was restored in the 1970s and decorated by contemporary artist Pierre Buraglio in 1992.