Leave it to the ingenious Germans to come up with a train door system which is virtually indestructible and will delight a railroad's bean counters by being inexpensive and imminently durable. Behold the Ytong block and cement door:
Seriously though, this is what employees of the Hamburg S-Bahn system found on one of their trains this morning. Unknown person(s) had used concrete blocks and cement to barricade a door on one of their trains. The Hamburg S-Bahn is apparently a bit tight lipped about where and when it happened, but the German Bundespolizei (the police department responsible, among other things, for policing German railroads) is investigating. No leads yet. The damage was estimated to be about 20000 Euros.
Here is a photo of a more pristine Hamburg S-Bahn train: