Lake Aydat, in the Puy-de-Dôme department, is a natural lake of volcanic origin. Like its neighbor, Lake of Cassière, it resulted from the obstruction of the Veyre valley by a nine miles long (15 km) lava flow called the cheire of Aydat, 7,000 years ago. It emanated from the neighboring volcanoes of Puy de la Vache and Puy de Lassolas. Lake Aydat is a eutrophic lake, characterized by troubled waters caused by a proliferation of aquatic plants.