This natural Icelandic fissure allows divers to swim right between two volatile tectonic plates.

This beautiful, historic church looks like something out of a simpler past.

The picturesque birthplace of Icelandic democracy is drenched in the blood of its brutal past.

Iceland's "Smoky Valley" is a beautiful river that is shrouded in a constant cover of steam clouds.

Walk in the footsteps of the gods and straddle two tectonic plates.

Medicinal spa created with the discharge from a geothermal energy plant.

This mountain fissure hides a secret path to a secluded mossy grotto within the rock itself.

A rare tour of a commercial jet assembly plant, held inside one of the largest buildings in the world.

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

A tunnel with windows, so you don't miss out on the impressive views.

The wild west is still alive and well at this authentic mining town watering hole.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

A sanctuary for sickly, stray, or wounded donkeys.

Celebrating the greatest pugilists the world has ever known.

World's largest herd of white deer populate a former U.S. Army depot.

A mine fire has been burning under the deserted town since 1962, but this church is still going strong.

The remnants of a wooden-hulled fleet built and abandoned in WWI, now home to a thriving ecosystem.

A former major munitions plant that has been converted into a sprawling art space.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.