Walk through depictions of the torture inflicted on those who go to Buddhist hell.

Popular tourist destination where witches in dark hats sell dried llama fetuses for good luck.

Since ancient times these picturesque springs have been providing bathers with healing waters.

Steaming blood-red hot spring from hell.

Volcanically heated hot springs.

A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Malaysian fireflies create a dazzling display as thousands light up in unison.

The world's brightest bioluminescent bay.

Tubing through a cave lit with glowworms is a magical underground experience.

This massive mushroom has spent centuries eating its way across a huge swath of Oregon.

A haunted hot springs hotel that went from healing retreat to asylum before it was restored.

This naturally-sourced hot spring is now home to a clothing-optional resort.

Hot springs monkey spa in the middle of Hell's Valley.

This iconic L.A. bookshop is housed in an abandoned bank—both symbolic and chic.

This hobbit-y little hot spring may be the oldest spring used by humans in all of Iceland.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

An Aztec snake god has taken the material form of an apartment complex.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

Eclectic collection of dark and macabre antiques.

A popular tourist cave with a dark past.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.