Buried five stories underground, this Soviet bunker is packed with gas masks and Cold War paraphernalia.

A top secret Cold War bunker hidden beneath a Latvian spa facility is now open for tours.

Virgil's many-mouthed gateway to the underworld.

Italy's "New Mountain" rose from the ground in a volcanic eruption in 1538.

A submerged archeological park still holds the wonders of a Roman Sodom.

A sulfuric hellscape in southern Italy.

The Emperor Tiberius' palace of debauchery.

Skulls from the plague of 1656 and World War II bombings are united by a cult dedicated to caring for the ancient dead.

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

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

Pompeii's less famous neighbor is still revealing her secrets.

The oldest volcanology research center in the world.

A beautifully well-preserved ancient Roman villa.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

A tiny rural community in Switzerland was home to one of history's most shocking murders, and led to the banning of Absinthe for nearly a century.

A spectacular cave and a beguiling lake.

A treasure trove of pathological, forensic, parasitological, and anatomical specimens.

The experimental test tracks of a retro-futuristic monorail still stand in the French countryside.

In legend, this ancient dolmen was said to have been created when a troll tried to destroy a church.

An archival collection of over 2,200 case studies which includes human brain specimens and tumor specimens.

This East German military command bunker was ready for World War III.

Rare signs of the former Soviet Union in the Caribbean, though not where you'd expect them.