An early 20th-century sanatorium, long abandoned and now being reclaimed by nature.

The highest point in Belgium is a staircase to nowhere.

A Belgian self-built tower inspired by the Bible and ancient civilizations.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

This historical Netherlands fortress still bears the marks of its single siege.

This massive collection of taxidermy is full of specimens collected by missionaries during their international travels.

This vast World War II defense line was the site of a fierce battle.

The tallest waterfall in the Netherlands is a lovely, stepped feature that is only 50 feet tall.

This formerly-prosperous Silesian mining town was completely demolished in the late 1960s and early 1970s as an attempt to cover up a secret Soviet uranium mine.

This mysterious and once-grand memorial still embodies a remarkable architectural vision.

This unusually shaped mountaintop tower looks like a UFO floating over the city.

Tall columns of volcanic basalt make up this improbable-seeming rock formation.

This village in Bohemian Switzerland hosts more than 300 wood carvings inspired by fairytales, folklore, and other oddities, as well as a series of Communist-era tanks

An ornate century-old elevator still connects the two halves of Bad Schandau.

Ruins of a German castle on top of a towering stone pillar.

A Neolithic celestial calendar standing in a nondescript wheat field.

The only bicycle museum in the Netherlands charts the invention of the now-ubiquitous two-wheeled machine.

One of the largest sandsculpture installations in the world, this exhibit boasts a unique combination of sprawling sand scenes, theological musings, and salvaged shipwrecks.

This abandoned but well-preserved Prussian fortress sits abandoned in a Polish forest near the German border.

Where the interconnection of German power grids should be.

This public park collects signposts and other memorabilia related to local history, Polish-German relations and human progress

One of only two places in the world where two rivers cross each other without the waters mixing.

The oldest wind turbine in Europe, constructed by a group of friends in 1932.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".