Honestly I would go for the "man impaled on spike" idea. If they sacrifice like that to the gods in the future then they deserve what's coming to them.

Combine that with things that we have deep evolved fears of: Snakes, spiders, scorpions and others and I can't see why they would enter a site containing statues of all things associated with death. Sure, an Indiana Jones or a couple of hundred would die, but as long as the shielding is thin enough to inflict a quick death I doubt many would try to copy them.