The church of a Benedictine abbey (following the Clunaic order). An aisled transeptless basilica terminated to the east in a hemicycle with five shallow radiating chapels and ambulatory; the axial bay is wider (like Saint-Martin-des-Champs). The chevet of St-Leu with its shallow chapels refers both to St-Denis and to Senlis Cathedral; the plan and dimensions are particularly close to the latter. Unusual at S-Leu is the high chapel (added) over the axial bay of the hemicyle and the middle level of the elevation that looks so much like a gallery but is in fact a triforium.