Sure, there aren’t any dark spots left on the world map anymore. Centuries of exploration and satellite photography took care of that. But that doesn’t mean there isn’t still adventure left to be had. The world is host to many wonders, just waiting for you to experience them. And we don’t just mean the pyramids, or the Acropolis, or any number of other well-trodden tourist destinations. Sure, those are amazing. But wouldn’t you rather stumble upon something remarkable that everyone and their grandmother hasn’t already seen in a book? This subterranean wonderland in Cuba is a little-known gem that will blow your mind, but won’t blow your wallet to visit.