In context of overlay "Objets" – Fontaine – https://osm.org/node/13835125170 via StreetComplete_ee 63.1:

Bassin de Péchafilou

Attached photo(s):
https://streetcomplete.app/p/344942.jpg
https://streetcomplete.app/p/344943.jpg
https://streetcomplete.app/p/344944.jpg