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

Climb to the top of its spiral spire for spectacular views of Copenhagen.

An enormous playhouse designed to look like 21 stacked Lego bricks, with another 25 million colorful Legos inside.

A natural wonder in south Denmark.

This colorful artistic feature atop a Danish art gallery allows visitors to stroll through a rainbow.

This sublime architectural marvel is a rare example of an expressionist church.

Norway's national monument to fallen seamen.

The design of this beautifully crafted building was inspired by Norwegian glaciers.

The world's largest underwater restaurant is submerged off the southern tip of Norway.

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

This World War I fortress is the perfect place to catch a Montenegrin sunset.

A curious cave church carved into the face of a cliff.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

Inside the Šomoška National Nature Reserve exists a unique rock formation rarely seen in the world.

This "mathematical tower" was an observatory, early skyscraper, and place to reflect on all of nature and the cosmos.

This spire on an Austrian mountain is wrapped around a long spiral slide and has the world's tallest wooden observation deck.

Visitors dip into a variety of pools of what was once ice.

Ride a dragon train into a world of dwarves.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

Baroque celebration of the end of the Great Plague of Vienna.

A centuries old castle atop a dormant volcano houses museums devoted to both women and witches.

Each year melting snow turns these Austrian hiking trails into scuba zones.

Europe's largest dinosaur museum was founded by a passionate autodidact.