An operating limestone quarry.
Also erroneously called "Fond des Vaux" (the correct name "Fond des Vaulx" is given on http://www.cfv.be/fr/, the website of the company operating the quarry).
Refs.:
geonieuws-1982-10-achterzijde-belgie-wellin-resteigne
http://www.strahlen.org/vp/be/wellin/
http://www.cfv.be/fr/
- Neutkens, H. & Orinx, M. (2007): Neu und Schön: Calcit und Fluorit aus Belgien. LAPIS 32 (2), 13-18