An underground city of salt.

Countless stories attempt to explain Poland's mysterious J-shaped trees.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

Twelve sweet, nutty, life-sized statues are housed in this second-story shrine to almond paste.

Nestled within a German forest is an intriguing, growing rock.

The zoological collection at the Hessisches Landesmuseum hosts some of the world's oldest habitat dioramas.

These tenacious 14th-century towers defied demolition and are now a fairytale vacation rental.

A surprisingly detailed model of one of the most powerful telescopes in the world.

This famed marionette theater and museum is bursting with imaginative string puppets.

The atomic museum in the basement of this German castle displays long strands of replica uranium cubes.

In this brilliant blue spring in Germany, legend has it that a sad mermaid learned to finally laugh.

The mass grave of the 27 victims of the "Vampire of Hanover."

A beautiful collection of taxidermy birds and rare pomological wax models.

This old wooden funicular railway leads to a cemetery in the forest.

This German "living museum" is maybe a bit too immersive.

The only microgravity tower in Europe can produce nine seconds of weightlessness.

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

This historic little railroad runs through some of the most beautiful scenery in Germany.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

Every hour the doors open to reenact the legend of the heroic mayor who saved his town by drinking a gallon of wine.

Constantly maintained, this organ is playing a six-century long composition by John Cage.

A preserved Nazi labor camp now has a Holocaust museum on site and memorials to the thousands that died while imprisoned at the camp.

An amusement park on the grounds of an unused nuclear power plant, with a swing ride inside the cooling tower.

As lake waters recede, a German village reemerges after more than a hundred years.