The world's largest model of our planetary system.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

Thousands of well-dressed mummies below a monastery.

A sulfuric martian landscape that looks far better than it smells.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

The composer did some of his finest work in this country home, including "The Nutcracker."

Fascinating early attempt at a Jewish autonomous settlement.

The largest Buddhist city in Europe is a haven for chess fanatics.

Gargantuan home of Russian science.

Stalinist skyscraper built with help of cryotechnology.

The tallest hotel in Europe.

Hidden in a metro shop under a shopping mall, this small museum tells the story of one of the world's largest urban transit systems.

The past, present, and future of Russia's signature alcohol is remembered in the world's only museum dedicated to the starchy spirit.

Some of the world's only freshwater seals live in one very special lake in Russia.

Museum celebrating the achievements of the Soviet space program.

This ancient village and its adjoining cemetery have a beautiful history of death and remembrance.

Dr. Strangelove-esque tours reveal the inside a bunker once reserved for Stalin himself.

The secret cells in the basement of the KGB's Estonian "Grey House" have been preserved as a grim Cold War museum.

"There's nothing there," and other lies the KGB told us.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

This Costa Rican topiary park is a surreal garden of unearthly delights.

These mysterious ancient stone spheres were created by a civilization lost to time and are now mostly lawn ornaments.