Although the Netherlands are popularly assumed to be flat, this is really only true of Holland. To the south of the country are significant hills and Maastricht has its own ‘mountain’, St Pietersberg. Beneath it lies an immense underground stone quarry, which measures around 4 kilometres from north to south and the passageways within originally extended to hundreds of kilometres.
The quarry well pre-dates the Belgian border of 1839 and so an international border runs through the quarry. Many areas are now collapsed or unsafe and some areas have been destroyed by open-casting but a huge amount remains. The northern area of the quarry lies wholly within the Netherlands and can be visited on an organised tour.
Quarry tunnels are up to four metres wide, and six to seven metres high. The building-stone was removed by sawing it out with long, heavy saws. The bed nearest the ceiling was quarried first, after which one bed after another was taken up from the floor. Flint, which occurs in bands, appears often to have been left underground as useless. Score-marks on the quarry walls may be seen where the axles of carts have worn into the stone. As well as saws, long chisels were used to free blocks of stone from the quarry face. These, too, have left characteristics tool-marks on the stone.
In 1928 a narrow-gauge railway tunnel (the Van Schaik tunnel) was driven east-west through the northern part of the underground quarry tunnels complex. This allowed electric locomotive-hauled trains of wagons to serve a small cement works in Jekerdal, linking it with the former Maastricht Canal alongside the Maas on the east side.
Further excavation took place adjacent to the Van Shaik tunnel in the late 1930s when a secure vault (kluis) was excavated for the storage of the country’s art treasures. Here, well away from prying eyes, masterpieces from the Rijksmuseum including The Night Watch spent World War II. The vault is in a remarkable state of preservation and a highlight of any visit.