One of the world's smallest prisons boasts just two small cells.

This remote church calls a tiny island its sanctuary.

It's believed that this small church was connected to the Hagia Sophia via a secret tunnel.

The site where a plot to assassinate Hitler was planned—and its conspirators were executed—is now a powerful memorial to the German resistance during World War II.

Turkish adventurer antiques in the heart of the Grand Bazaar.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

This once-grandiose behemoth of a monument from the socialist era now sits quiet and closed up.

Founded in the 4th-century, the town of Pernik plays host to the Surva Carnival⁠—a magnificent display of masked Kukeri dancers.

The second-highest train station in Europe.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

The art museum is decorated with creatively remodeled pre-Nazi swastikas.

A novel collection of medical curiosities housed in an 18th-century surgeon training academy.

This sublime architectural marvel is a rare example of an expressionist church.

A museum that chronicles the history of the Nuremberg Trials for Nazi war criminals in the building where the trials were once held.

Once the tallest building in Chisinau, this unique tower is a relic of Soviet architecture.

Artfully arranged bones of 5,800 Austrians.

A saintly relic hidden in a Prague church basement.

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

These elaborate gothic monuments honor Verona's medieval lords.

A crucified and bearded female saint.

An existential riddle in the world's largest ancient castle.

A Jenga-style cylindrical tower of books that appears to go on forever.