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. The commune sits on a Lutetian sedimentary limestone plateau covered by Chantilly Forest. Sand created by wind and erosion covers this chalky plateau. Although the sand is less than a meter thick it is very useful for training horses in the forest. This stone has also been used for building in parts of the region, and still is today in the adjoining commune of Saint-Maximin. It was also used for building in Chantilly itself during the 18th century, when a quarry on the current site of the racecourse produced stone for the court officials' housing and the stables. In the following century the quarry was used to grow mushrooms, then as an air raid shelter during World War II. It now belongs to the Chantilly Estate and is periodically open to the public. Another geological feature is alluvial accumulations in the river valleys, which have allowed, in the case of the Nonette, the development of community gardens in the locality known as the Canardière. Hydrology and water supply The town is bounded at its southern edge by the Thève, a 33 km-long tributary of the Oise River. At this point that valley contains the Commelles ponds, created in the 13th century by the monks of Chaalis Abbey to stock fish. The river Nonette runs through the town itself. This 44 km-long river is also part of the watershed of the Oise and is channeled into canals throughout the municipality. In fact, the creation of the château gardens by André Le Nôtre required the complete transformation of the waterway starting in 1663. The riverbed was moved a hundred meters north to create the 2.5 km-long Grand Canal that runs in front of the château. The old riverbed became the 800m-long Canal Saint-Jean, named after a 16th-century chapel demolished when the gardens were created. The Canardière, beneath the actual viaduct, was channeled and cleaned up at this time also. The Canal de la Machine, perpendicular to the other two and nearly 300 meters long, brought water to the Pavilon du Manse, which fed it