This Vietnamese hell cave lets visitors take a walk through a devilish underworld full of demons.

This monastery built into a cliff hides a perfectly preserved hermit in a glass coffin.

A stunning 18th-century site where pilgrims ascend by a series of punishing stairs only to return via funicular.

This castle has links to Portugal’s founding and struggles for independence.

A remnant of the Roman army's presence on the coast of Scotland.

Aside from denoting a public square or market, this medieval structure was also a sign of a town's prosperity.

Abandoned boats decaying in the largest ship graveyard in mainland Britain.

Underneath the historic center of Mexico City, the remains of a temple dedicated to the Aztec god of the wind.

This awesome Spanish castle is so fantastical it was actually used on Game of Thrones.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

An open-air museum showing how people on El Hierro lived from the time of the first settlers until the late 20th century.

Teeny tiny hotel on the coast of the Canary Islands.

How this choice of tombstone came to be is still a mystery.

One of the last designs from architect Oscar Niemeyer.

An eccentric memorial garden to the "warrior" birds of World War I, the messenger pigeons used by the Allied forces.

This king penguin is a knighted brigadier of the Norwegian Army.

Home to the oldest operating roller coaster in the Southern Hemisphere.

Personal garden filled with mosaics made of recycled garbage.

One of the oldest and largest wooden churches in France was very evidently constructed by shipbuilders.

The walls of these four caverns are filled with art that dates back to the earliest human presence in Europe.

A potpourri of rocks, fossils, and crystals is rounded out by a dinosaur garden and a 15-foot great white shark.

Chef Lawrence West serves up Indian tacos, wojapi, and other Lakota dishes at the brick-and-mortar incarnation of his popular food truck.

Home to one of the most popular teams in Scottish football history.

Before it was buried by volcanic ash, this fast-food restaurant fed the hungry hordes of ancient Rome.