This now-abandoned outcrop is an important Native American spiritual site, overtaken by European settlers and mining pollution.

This tea house was a hand-built gift from Boulder's sister city in Tajikstan.

This deserted Gold Rush town is home to a Masonic lodge that, strangely enough, still holds meetings.

Toss a Frisbee through the ruins of this Colorado gold mining town.

A beautiful combination of living flora with preserved bones covers the shelves of this shop.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

It's easy to forget what century it is as you wander this rustic homestead.

A technicolor place of worship for Elevationists.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

Jesus' footprints and the first catacombs in the world.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The underground sanctuary of a mysterious ancient cult.

The yawning maw of this pagan visage is said to bite off the hands of liars.

This curious, round temple is the oldest still-standing marble building in Rome.

A burial vault located under Tiber Island in the middle of the Italian capital.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

The oldest stone house in Paris was built by its most famous alchemist.

Longest canal tunnel in the world, abandoned in the 1960s.

An abandoned relic of the city's failed experiment with below ground transit.