One of the coolest “tourist-y” things to do in Maastricht is the tour of the Northern Caves under St. Pieterberg hill.
On top of the hill itself there is a fort (Fort St. Pieter) built in the 1700s. It sits on one of the highest points of the city – making for some great photographs!
The tour we took was of both the fort and the caves spanning far underneath. The caves are something else entirely – they’re man-made, and so easy to get lost in. While I didn’t take pictures (or at least none that turned out ok), you can find some on trip advisor. The caves are a labyrinth of more than 80km under Belgium and the Netherlands, and include an 18th century shelter, old mines, an explosion dome, mushroom growers and National Storage Facility no. 9 which protected Dutch national art treasures during World War Two.