Chantilly straddles the junction of the Paris Basin and the western County of Valois, of which the Nonette river is a boundary. The site of the town was originally a clearing or meadowland, sometimes called a lawn or "pelouse", which is mostly occupied today by the racecourse. The remaining open space between the town and the racecourse is always referred to as the "little lawn". The highest point in the area, 112 meters, is at Bois Lorris, in Lamorlaye. The lowest elevation is 35m, at the Canardière on the banks of the Nonette in Gouvieux.