This remote islet, wedged between two banks, rises to an altitude of 700 metres. Listed as a historical monument and a site of outstanding natural beauty, it contains the remains of a former prison colony for children built in 1864 and run by the Pères de la Congrégation du Saint-Esprit until it closed in 1879. In 2019, a LiDAR survey helped detect and map the archaeological remains on this unique site, the subject of an archaeological and historical study in 2020.