The 'Eglise de Champaubert' is the church of one of the three villages Champaubert, Nuisement, and Chantecoq
that were submerged by the construction of the lake. This church was protected from the waters by building a dam at the edge of the lake.
https://www.desyeuxplusgrandsquelemonde.com/les-villages-engloutis-du-lac-du-der