Enormous burial mounds of ancient emperors.

A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

The most famous location in China was home to whole dynasties worth of imperial rulers.

Stalinist skyscraper built with help of cryotechnology.

Gargantuan home of Russian science.

The tallest hotel in Europe.

Former headquarters of the KGB.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

The roof of one of the world’s largest spice markets provides a grand view over the neighborhood's glorious bustle.

A favorite haunt of Delhi's politicos and intellectuals, this old-school coffee shop was shut down under Indira Gandhi's Emergency.

An early 20th-century bullring converted into a modern shopping center.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

A small museum in the Bay of Pigs gives the Cuban perspective on the famously failed U.S. invasion.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.

A focal point of the Cuban government, this city square features one of the most iconic images in the country.

A colorful narrow alley in Cuba is full of street art and sculptures made of found objects.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

One of the world's largest collections of pathological specimens.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

A preserved college lock-up that recalls a clubhouse approach to discipline.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

It's good luck to be mocked by this monkey.