An open-air sewer system that was covered piece-by-piece over 300 years.

The patron of this extravagant Art Nouveau confection insisted that nothing less than a boat should project from its facade.

Rare wooden escalators lead deep down into an otherwise staggeringly monotonous tiled tunnel.

Peek into a cave of giant, glimmering crystals.

An eccentric 18th century naval officer built a ship's quarterdeck on his roof, the inspiration for Mary Poppins's "Admiral Boom."

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

The commemorative stone column conceals a secret laboratory.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

Ancient serpentine sacrifice holder that has stood the test of time.

A fountain standing as a testament to a doomed alliance.

Step back in time and witness the fall of Constantinople.

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

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

A marvel of Byzantine engineering under the streets of Istanbul.

This faux-seedy Japanese arcade is made up to look like a maze of alleys straight out of a cyberpunk dystopia.

The world's shortest escalator doesn't seem to have any reason to exist other than to hold a world record.

After being lost for decades, this striking mural depicting the atomic bomb covers the wall of a busy Tokyo metro station.

Go through the looking glass in Tokyo's Wonderland-themed shop.

The original "capsule building" is a masterpiece of Metabolist architecture.

Japanese island famous for poison gas and fluffy bunnies.

Peace Park and the Atomic Bomb Dome.

Japanese national treasure originally built in 593 CE.

Devoted Buddhists can earn enlightenment in the next life by crawling through this symbolic nostril.

Largest graveyard in all of Japan surrounds a famous mausoleum.