The patron of this extravagant Art Nouveau confection insisted that nothing less than a boat should project from its facade.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.

A rare example of World War I trenches from the British front.

A little sculpture with a large wardrobe.

Hiding the longest subterranean river known in the world.

A magical and peaceful ruined Cistercian abbey in what is now southern Belgium.

Climb inside an iron crystal magnified 165 billion times its normal size.

This fairytale castle was built as a show of power but was nearly torn down thanks to its history of torture.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

The last bastion of Roman presence north of the Alps looms over a German town.

Hamburgers are intensely proud of their tunnel beneath the river.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

Berlin's old airport.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

One in a pair of subterranean caves created by an ancient eruption of Mount Fuji.

An eerie reminder to the horrors of World War II.

This 14th-century temple is also known as the "Temple of the Golden Pavilion" for its gorgeous gilded reliquary hall.

This little replica of Lady Liberty provides a bit of NYC in a Japanese city.

Paris' fabled purveyor of exotic taxidermy and natural history curios.

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

Lavish royal estate punctuated with heated greenhouses.

Down a cobblestone alleyway is a museum dedicated to Romanticism, with a secret garden.

Once a black market electronics marketplace, now an otaku shopper's paradise.

The quintessential Japanese rock garden has existed for more than 500 years.