A subterranean Holocaust refuge within one of the world's longest cave systems.

From Coke II to Google Glass, this exhibit features some of the most spectacular commercial flops.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

Site of the world's largest nuclear explosion.

Former prison camp dedicated to the victims of political repression.

The deepest hole drilled in the name of science, where evidence of Precambrian life was found.

A remote forest of stone pillars along the Lena river.

The world's second-largest excavated hole.

Secret Soviet city once home to Russian cosmonauts and space training facilities.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

A top-secret bunker now turned museum, is an eerie look at what life would have looked like in the event of nuclear war.

Ample proof that watery ends make for well-preserved, millenia-old mummies.

Explore the complex ecology of this multifaceted nature preserve by riverboat.

The patron saint of spinsters grasps a container of dried blood.

The 1936 Summer Olympics site is a crumbling remnant of sportsmanship and a history its host country would like to forget.

Skeletons dressed in extravagant 18th century royal costumes cavort in the aisles of this German basilica.

The oldest church in the Estonian capital is home to over 100 fantastical cemetery coats-of-arms.

Only a fragment of this 15th-century Dance of Death survives today.

A secluded art gallery hidden within the cellars beneath Tallinn’s medieval monastery.

Disused seaplane hangar gets a second life as the jaw-dropping home of Estonia's museum of maritime history.

The Devil’s own choice when he needs a drink in Brussels.

Inside the corridors of this flea market, visitors are sure to find some obscure and odd treasures.

Archduke Ferdinand II's collection of rare objects is considered one of the oldest museums in the world.