Volcanos are usually things to be admired from a safe distance, but inside of most everyone is an excitable inner voice that really just wants to climb into that caldera and see what it's like inside. Iceland's Thrihnukagigur Volcano actually lets adventurous spelunkers live out that adolescent dream. 

Last erupting over 4,000 years ago, the three calderas of Thrihnukagigur Volcano have lain dormant for so long that one of them is even safe to climb into. Unlike most dormant volcanoes which simply cool with their previously roiling ocean of magma in place, creating one solid plug, the fathoms of magma that once boiled inside of one of Thrihnukagigur's peaks seem to have simply sunk back down into the earth, leaving a massive, stunning cavern.

Hiking out almost an hour into the Icelandic highlands, visitors can now approach the open summit and descend hundreds of feet into the main magma chamber via a cable lift. The main chamber is so large that according to the website, it could house the Statue of Liberty in its entirety. The craggy walls of the cavern are not the jet black obsidian that one might expect either, but instead they are covered in a gleaming pearlescent rainbow of colors that almost make the cave look as though it is made purely of gems. 

Each excursion into the volcano's depths lasts around an hour or two, making the experience a bit truncated considering how incredible a feat it is to literally lower one's self into a what was once one of the most impossible to reach locations on Earth.