Climb to the top of one of those gigantic Redwood trees they have in California and stuff. Supposedly, they're large enough to be ecosystems of their own.
I'm not talking 'technical ecosystem', I mean they have caves up their. Berry bushes growing out of the tree, little ponds formed from rain water.
I don't know if this is entirely true, but if it's even partially true it would be ... astounding. Definitely worth the climb.