Here is another installment of exTRAPaganza, our Thursday over-the-top trap series.
The exit to the cave is blocked by a huge boulder. After some investigation, it appears that the rock can be tipped over by some special machinery towards the top by a single character. The floor of the cavern is actually somewhat springy, but it takes something very large, like a very big rock, to notice. When the rock is toppled, the floor acts like a trampoline, hurtling the party into the craggy ceiling.