At around 5100 BC, the first Neolithic groups settled in the Paris Basin. Archaeologists have found a few tenuous remains of them at the site of "Basses Coutures”. During the construction of the A16 motorway, pits and three graves—containing a man, woman and child—dated to the Early Neolithic (5100-4700 BC), had already been excavated in Champagne-sur-Oise.
At around 4500 BC (Middle Neolithic), the megalithic phenomenon emerged. It is associated with the construction of funerary monuments reserved for a few individuals. In the Val-d’Oise, at the end of the Neolithic (3500-2000 BC), monuments known as "gallery graves” sometimes contain the remains of several hundreds of individuals, as at Guiry-en-Vexin. These "gallery graves” are the most numerous megalithic monuments (15 cases), but some researchers believe that 4000 years ago, more than 300 of them existed.
There are many fewer megaliths in the Paris Basin than in other regions, such as Brittany and Languedoc: 21 monuments are currently standing in the Val-d’Oise, and 18 others have been destroyed since the beginning of the 19th century to produce paving stones for streets. Menhirs are less frequent, with 5 known in Cergy, Menouville, Chars, Ennery and Jouy-le Moutier. These are most often located near water.