A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

A former hen house turned curiosity cabinet displays one man's lifelong fascination with cannibalism.

The world's largest maze is a nature park with nearly 200 decision points.

Preserved "bog person" that is over 2,000 years old.

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

Old Danish castle immortalized in Shakespeare's Hamlet.

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

A peat bog in southern Sweden provides a cozy and photogenic home for junked Volvos, Saabs, and the occasional American muscle car.

A walkable map of the world, made from soil and stone by one man.

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

A botched 18th-century canal silenced one of Sweden's most magnificent waterfalls.

A man has revenged his true love's betrayal through tears and stone genitalia.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

In legend, this ancient dolmen was said to have been created when a troll tried to destroy a church.

Hundreds of mossy stones engraved with bits of philosophy, literature and random musings.

Dozens of musicians have planted trees in this Danish park, and donated songs to go with them.

This Danish rock field is actually a sprawling ancient cemetery holding the bodies of 700 Vikings.

This pyramid in southern Sweden houses the remains of an eccentric nobleman, who spent his life doing whatever he felt like doing.

Iron Age grave stones and Viking burials, a short drive from Gothenburg.

Bring your hiking shoes, wool socks, and thermal underwear for a stay in these cozy forest huts.

Research station devoted to mysterious floating lights seen in a Norwegian valley.

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

An abandoned lighthouse awaits its destiny: being buried under shifting sand.

The last fully functional fortress of Germany's World War II Atlantikwall.