St Pietersberg Caves

To the south of Maastricht are the St Pietersberg Caves, a widely ramified system of tunnels and passages, formed over many centuries by the quarrying of the local marlstone, which provided shelter for the inhabitants during the town's many sieges. Originally there were some 20,000 passages with a total length of 200km/125mi. During the Second World War some of the passages were enlarged, a well was dug and storerooms, a bakery and even a chapel were constructed, providing accommodation in which most of the town's population could take refuge and live for a considerable period.

Since the rocks were formed on the bottom of an inland sea large numbers of fossils can be seen in the walls of the caves. The constant low temperature in the caves, shut off as they are from any strong inflow of air, provides ideal conditions for mushroom growing. There are regular conducted tours of the caves.