Tubing through a cave lit with glowworms is a magical underground experience.

These two delightful animal-shaped buildings host a visitor center and wool shop.

This electric green sulphur lake in New Zealand looks like a cartoonish radioactive dump site.

Deadly scalding and one of the largest hot springs in the world.

The once and future home of New Zealand's famed Pink and White Terraces.

Major tourist destination known for its bubbling mud-pools and hot thermal springs.

The explorer Captain Cook may have named it White Island, but the Maori call it Te Puia o Whakaari – The Dramatic Volcano.

Super-heavy Nazi architectural experiment.

Berlin's old airport.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

A castle-like sea fort from the 17th century is now a museum to oyster farming.

A quarry cum sculpture park where the works of art are chiseled into the very walls.

Fighting the British and making game shows for over 150 years.

A perfectly circular stronghold constructed in the 10th century is now a nucleus of Viking culture housing a museum, village, and reenactment of an epic Viking battle.

This museum is a portal to 20th-century Denmark.

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

This demon atop the Notre-Dame de Paris looks utterly bored.

This modest marker near Notre Dame identifies the very center of Paris.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

The celebrated eyesore created by starry-eyed sweethearts.

This bridge was constructed from the rubble of the infamous Bastille.

The water-powered carriages are long gone, but for over a century this funicular railway has been the fastest route to the highest point in Paris.

135 bronze medallions mark a French meridian line which once rivaled the hotshot Greenwich timeline.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.