Slate Museum and underground quarry, Haut-Martelange (Musée de l'Ardoise)

What it offers

An open-air museum of the old slate quarries at Haut-Martelange, right on the Belgian border. The site has 22 historic buildings, exhibitions, a small bistro and the Johanna underground quarry, 42 metres down and 370 steps, where it stays at 9 °C all year. Walking around the grounds is free. For families, friends or on your own; the underground quarry is from age 4.