ShotHotspot has mapped 26 abandoned places in Bretagne, France, ranked by how often they're photographed, viewed and voted for. The most popular are Forges Trignac Urbex Abandoned, Viaduc de la Verrière and Anciennes Tanneries Sylvain Brajeul. Some are private property or unsafe, so get permission before you visit.
We don't know whether you're allowed to visit any of these places. Many are private property, closed to the public or unsafe: get permission from the owner or the relevant authority, and take safety precautions.