This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

An intricate ceramic tile facade adorns this five-star hotel.

Eat your way through history.

An abandoned saucer-shaped monument in the Bulgarian mountains.

This hidden garden boasts amazing views of Lyon.

Inside this museum, Christians were imprisoned when the Romans controlled Gaul.

This 8th-century Bavarian monastery is home to an exquisite Baroque-era library.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Overlooking the harbor is a beautiful neglected mansion guarded by two Egyptian sphinxes.

A spectacular cave and a beguiling lake.

Ruins of a 13th-century fortress perched above a breathtaking Mediterranean bay.

This former luxury resort in Kaua'i is now an abandoned relic.

This ruined fort and statue are a testament to the last king of Kaua‘i’s savvy diplomacy skills, which briefly brought Russians to Hawai‘i.

This narrow coastline trail through the dense Kauai wilderness is among the most beautiful and dangerous in the world.

This WWII plane died a quiet death, and is now a garden eel playground.

A top secret Cold War bunker hidden beneath a Latvian spa facility is now open for tours.

The 19th-century home of Count and Countess von Hallwyl is now a museum.