The Lot river rises in the Cévennes, flowing west through Quercy. It flows into the Garonne near Aiguillon after 480 km. The Garonne river rises in the Val d'Aran in the Spanish Pyrenees. After 575 km it meets the the Dordogne and forms the Gironde estuary.
Both rivers are important for the underground sights of the département, as they cut through karstified limestone hills with many caves. During the Stone Age they were important hunting grounds for our anchestors. Even during the Ice Ages, they were enclosed by glaciers from the north and south, but not covered by glaciers.