Damn! Watch this railroad tanker car instantly implode:
I couldn’t find too much information on the source of this clip, but it appears to be part of a safety training video on the perils of improperly steam cleaning tanker cars. In the clip, the tanker car is filled with steam and the safety valves are disabled. The steam cools, then condenses, the pressure inside drops, and the pressure difference is big enough to crumple that huge railcar like a napkin.
Update: See also “sun kink”, when railroad tracks buckle in intense heat:
An explanation of the effect can be found here. (thx, will)