1 Prof. Jones: {running in front of the giant stone ball that is chasing them through the Vatican library} There's one thing I don't get.
1 Monty: What, dad?
2 Prof. Jones: This trap is completely wrecking the library.
2 Monty: And us too, if we're not careful!
3 Prof. Jones: Why build a trap that destroys what you're trying to protect along with the people trying to ransack it?
4 Monty: It's traditional!

This has always bugged me about those elaborate deathtraps you see in the movies. Not only do they threaten deadly peril to the heroes (or villains) who try to defy them, but they often seem to completely destroy the building, whatever they were in fact supposed to be guarding (if it hadn't already been removed), and several square kilometres of the surrounding rainforest.

If real ancient civilisations built deathtraps like that, there wouldn't be any ancient monuments or buildings left, since they all would have self-destructed as soon as a would-be robber entered the place.

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2018-03-21 Rerun commentary: I'm now imagining archaeologists coming across a huge pile of tumbled rubble in the middle of a jungle or desert somewhere. After years of painstaking excavation, they find buried under it all a magnificent piece of treasure, though crushed by the stones, along with the remains of someone obviously in the act of reaching out to grab it, and thereby triggering an obvious deathtrap that caused the whole structure to collapse on them.