The largest treasure hoard in Europe is contained in a castle that was bombed out during World War II.

A vast and unlikely aviation museum kept alive for over 50 years due to one man's tenacity.

A stone marker and sculpture in the city of Riga stake a claim for the very first community Christmas tree.

A hermit's tiny cell built into the cliffside that saved him in South Pembrokeshire.

His music once banned in Communist Cuba, John Lennon is now immortalized in bronze by Castro, who considers Lennon a "fellow dreamer."

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.

In terms of history and architecture, this is one of the most remarkable cemeteries in the world.

A Spanish-style estate that has traded black ties for rock concerts.

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

According to the Guanches, the aboriginal people of the Canary Islands, the king of evil lives inside this volcano.

Lava stone structures possibly dating back to the 19th century may have been a stopping point for voyagers between ancient Egypt and the Mayan Civilization.

A completely underwater art museum sends a stark message about humans' impact on the environment.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

The chefs at El Diablo use heat generated by an active volcano to cook the food.

Visit a surreal landscape so otherworldly NASA actually used it to train the Apollo 17 crew.

The world's tallest bridge is also possibly the most elegant.

The platform atop this verdant volcano was built with the help of a royal elephant.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

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

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

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

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

Opulence and fantasy collide in this royal chair which is supposedly made with unicorn horns.