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

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

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

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

This imposing memorial contains the remains of Che Guevara — and 29 other guerrillas who died with him in Bolivia.

Many Hindus make the long pilgrimage to this holy city to have their remains burned on the banks of the Ganges River.

The oldest still-inhabited hill fort in India looks like a magnificent golden sandcastle.

Once an indicator of social class, the color blue has come to define this city on the edge of the Thar Desert.

There are millions of temples in India, but only one prominent temple dedicated to the Hindu creator god.

This peaceful Sikh gurudwara serves around 50,000 free meals every day within its gilded walls.

A city entirely devoted to illegal gun production.

The former stronghold of the Malla Dynasty has remained virtually unchanged since the 17th century.

One of Ireland's most infamous prisons for rebels including men, women and children.

It houses the remains of a 17th-century version of the Titanic.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

Plundered and left asunder by grave robbers, this ancient necropolis has been painstakingly pieced back together.