grayscale photo of building

Traboule. Among a handful of cities traversed by traboules, Lyon is the most famous for its own. Traboules are hallways through private buildings which were usually used by silk manufacturers et al. to move their products while being sheltered from the weather caprices. Some are still open to the public a few hours a day... if one dares to push a few closed doors to find them. You can read more about this on Wikipedia: https://en.wikipedia.org/wiki/Traboule