There’s a touch of Jules Verne about the Grottes de Hotton. The deepest of the Ardennes cave systems, they’re well worth the short trip from la Roche – and not just on a rainy day, either. Tours last an hour and take you 75m underground, where a fast-flowing river pours through a canyon almost 40m deep and just a few metres wide – an awesome sight. There are stalactites and stalagmites galore, again among the best you’ll see in all of Belgium’s caves, including patches of rare and peculiar specimens that grow horizontally from the rock.
The caves are about 2km from the centre of the sprawling village of Hotton – they’re well signposted but only reachable on foot or by car; from the main riverside rue de la Roche, follow route de Speleo Club de Belgique.