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Mystery #3Tier 2caves and rock

How do huge caves hollow out deep inside solid rock underground?

Deep below your feet, in some places, there are caves big enough to swallow a cathedral, hidden inside solid rock. Nobody dug them out. There was no machine and no explosion, just darkness and slowly dripping water. So how do huge caves hollow out deep inside solid rock underground?

A vast underground limestone chamber with pale rock walls and hanging formations, lit from below
Photo: Cerevisae · CC BY-SA 4.0 · via Wikimedia Commons

Your guess

No machine dug these caves out. What do you think slowly hollowed them from the solid rock?

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