Caerse por una montaña o Caerse de una montaña . Would be the literal translation

If we use it for example in this phrase: '' You can't fall off a mountain '' Then the literal meaning of ''Fall off a mountain'' would be ''Caerse de una montaña''. But i don't know if you're looking for a more metaphorical meaning or something... Hope it helps!

Could you use it in a sentence?