The Association de Défense des Sources de Longpont offers a visit to a little-known heritage of Longpont, because underground: the network of sources, captured and led to the historic village from the old regime. The commented visit presents the Regard des Folies (monument inscribed in the additional inventory of historical monuments), where the water collection gallery arrives. It is preceded by a commented walk (about 1km, accessible to all) on the route of the network of captured springs arriving in the village of Longpont, where water appears in the light. This visit puts into perspective the history of the creation of Longpont and its development through the integration of its priory in the Cluny network. The network of sources is still functioning today and reflects the importance of the water resource and the know-how of its creators. Departure from the town hall in front of the Basilica of Longpont on Sunday at 10:30 am. Duration: 1h30 to 2am.