The silly symbol for an underground protest group is now scattered around the city.

Nearly 40 miles and 1,000 years of limestone mines under Denmark.

A failed attempt to control drifting sands yielded a gnarled sylvan wonderland.

The music is over at the Ballhaus Riviera Ballroom, but the ballroom remains in haunting disrepair.

Germany's last remaining Lenin statue has become a lightning rod of debate about the country's divided past.

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

The small alleys in Lübeck's Old Town are a result of medieval urban sprawl.

An abandoned town of skeletal wooden homes.

World's strongest whirlpool.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

Thousands of years of crashing waves gave this mushroom-shaped rock its svelte figure.

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

These Finnish rapids have been attracting tourists for over a hundred years and are now released with the push of a button.

Legend has this precariously placed rock was placed by giants. Science has another explanation.

Walk behind a 50-meter-high waterfall.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

Walk 2,300 feet above the ground on the "Troll's Tongue."

An intricately carved Viking church overlooks a glistening fjord.

One of the most breathtaking railways in Europe also takes one of the steepest climbs, from fjord to mountain plateau.

A thin pane of glass keeps visitors from sliding off this futuristic skywalk.

Denmark's famous pseudo-hill.

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

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.