This 18C church is built in the middle of the quadrangle formed by the old abbey buildings. After the dome of St. Peter's in Rome, and Les Invalides in Paris, this is the third largest dome in Europe. Inside the dome is a false cupola, suspended from the true dome although it appears to be supported by the columns of the central rotunda. Behind the high altar lies the chancel, which is quite long and roofed with cradle vaulting.