Happened to be in Geleen. It's not an old town, it grew mostly between 30's and 80's, due to the coalmines and a huge chemical plant. There is one old building however, this 1699 Sint Janskluis. A small chapel/church. In those dangerous times (there were bloody gangs, and a lot of foreign empires that had set their eye on these parts: Prussians, Austrians, Spanish, French, Holland) a building like this also served as refuge, hence the thick walls.