A small, wild-looking glacial lake, Lake Ilay occupies the Frasnois and La Chaux-du-Dombief communes, 800 meters above sea level, in the heart of the Jura department (Bourgogne-Franche-Comté). It stretches over the French Jura lakes region and is 1.9 km by 0.4 km long and covers more than seventy-two hectares.
Lake Ilay surprises with the color of its turquoise waters, as well as with its cliffs that extend in the distance. Also called La Motte Lake, it actually has an island in the middle. The latter is connected by a roadway today immersed. Archaeological excavations have revealed that the mound was inhabited in the Neolithic and that a monastery was installed in the eleventh century.
At a depth of ten meters and an elongated shape, Lake Ilay is mainly fed by Lake Grand Maclu to which it is connected by a small natural channel. It flows into the river Hedgehog, and is close to the Hedgehog waterfalls.
