A toxic ghost town sitting atop a massive coal fire.

This Prague museum collects brutalist relics and memories from the country's former Soviet rule.

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Macabre astrological automaton clock dating to the late 1400s.

This easily overlooked memorial immortalizes the scars from the 1956 Hungarian Revolution.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

On any given day this sprawling market houses literally tons of government-regulated gold, gems, and precious metals.

This artificial archipelago was supposed to resemble a map of the world.

Al Rahmah Mosque appears to "float" atop the Red Sea.

This historic hotel preserves many treasures from its heyday hosting passengers on the Orient Express.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

An abused and forgotten metropolis, abandoned for centuries.

The ornate miniature mansions were built for Istanbul's feathered residents.

A marvel of Byzantine engineering under the streets of Istanbul.

In this historic region, homes and churches are carved into ancient volcanic rock formations.