Be aware that climbing outside (buildering) in areas that are not explicitly "tolerated" or "designated" may be unwanted or illegal.
Hier zijn de bunkers goed te vinden: https://www.openstreetmap.org/node/2312145783#map=16/52.0991/4.3354
Did you know that you can create an account to record, track and share your climbing ascents? Thousands of climbers are already doing this.
Check out what is happening in Bunkers Clingendael.