Grand-Hornu in Boussu

You're standing at Le Grand-Hornu, an old coal mining complex in Hornu, just outside Mons. Start with the entrance and its three arches. Behind it lies a square forecourt, where the horses were stabled and the hay and miners' lamps were stored. Further on you reach an oval inner courtyard. Arches, pediments and half-round windows: it looks more like a palace than a mine.