Gemeentegrot in Valkenburg aan de Geul

You're standing at the entrance of the Gemeentegrot in Valkenburg, at the foot of the Cauberg hill. Take a look up. On top of this hill sit the Polfer woods and the Holland Casino building. And underneath it runs a huge maze of tunnels. It isn't really a cave, by the way. It's a quarry. For centuries, stone cutters hacked marl out of this hill, a soft kind of limestone.