The Église St-Germain-des-Prés was once the church of a Benedictine abbey founded in the 8C. Only the sturdy tower on the façade remains from this earlier structure (the spire is a 19C addition). Inside, the Chapelle Saint-Symphorien was once part of a Merovingian sanctuary. Note the funerary stones of Descartes, Mabillon and Boileau, as well as the tomb of Jean Casimir, the king of Poland.