This Polish cave has housed a dragon, a brothel, and an enduring legend.

An underground city of salt.

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

A naturally occurring tunnel in this Nordic mountain makes it look like it's been shot.

What might look like a cliffside sacrificial altar at first glance is actually a stone compass pointing to cities and lighthouses all around the world.

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

The world's northernmost aquarium looks like it has fallen over.

According to the locals, the sands of this secluded Norway beach are infused with gemstone particles.

At the very tippity-top of Europe is a cliff from which you can view the midnight sun.

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

Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

Across the Pacific in a raft, a museum dedicated to Thor Heyerdahl's now legendary expedition.

Monuments don't get much more metal than these three giant viking swords planted in a Nordic hill.

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

Walk behind a 50-meter-high waterfall.

The convergence of two currents makes this a surprisingly pleasant getaway in the Arctic Circle.

A stunning silver lining to global warming's gloomy cloud.

A serpentine highway twists and turns over the treacherous Norwegian Sea.

The world's longest wildlife overpass provides Hilversum's critters with a safe alternative to trying their luck on the roadway.

The 20-mile causeway that separates the Netherlands from the sea.

The gargoyles and grotesques of the 21st century are here—22 emoji built into a new building in the Netherlands.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

A true Valhalla for cactus and succulent lovers.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.