A bibliophile's heaven that contains hundreds of bookstores, offering over a third of secondhand books for sale in Tokyo.

Five miles of underground river link lake to ocean.

Some locals believe the fabled lost gold of General Yamashida is hiding somewhere beneath the city.

An island in the middle of a lake, in the middle of a volcano, in the middle of a bigger lake, in the middle of a bigger island, in an archipelago, in the Pacific Ocean.

An eatery in a shallow river where diners can enjoy their meal mere feet from the base of an artificial waterfall.

A magically clear, blue river that seems to spring from nowhere.

Gardens representing parts of Asia, Europe, and the Mid East are tucked away among the Soviet-style buildings in East Berlin.

This Berlin island is home to a flock of free-roaming peacocks, as well as a historic ivory folly.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

Started as a kitchen garden, now the second largest botanical garden in the world.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

The most visited, and possibly most controversial, museum in Germany.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

A German apartment building hosting as many trees as human occupants.

This small town in the Netherlands has no roads but instead, miles of canals and over 100 bridges.

Futuristic apartment blocks are the backdrop for Montreal surfers hangin' ten on the Habitat '67 standing wave.

A grand Gothic Revival basilica with stained glass depictions of Montreal's religious history has only one soul resting in its crypt.

Hidden within a Netherlands crater is a stone bed that lets those who lie in it see the sky as a curved surface.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

On Japan's Tashirojima Island, cats are king.

A true treehouse near Hawai'i Volcanoes National Park.

A tunnel of hardened lava along Maui’s famous Road to Hana.

A Hawaiian stairway to heaven—that you can't climb.

Famously misunderstood wonder of the ancient world