The abandoned mine where American troops discovered a treasure trove of art and artifacts hidden by the Nazis.

Martin Bricelj Baraga's monolithic sculpture measures the blueness of the sky, and changes color to match it.

A plaque commemorates the spot in the Oregon woods where the first-ever Geocache was hidden.

A perilous medieval road leading right into the sea.

An institution dedicated to curiosity, logic, riddles, and Mongolia's long history of puzzles.

About 80% of all U.S. avocados are descendants of Rudolph Hass's glorious tree.

The Arctic Circle runs through this isolated spot north of Iceland.

Trace the history of writing at this unusual North Carolina destination.

An absolutely beautiful 200-foot stained glass installation traces the evolution of knowledge.

This cuddly rodent has a place of honor at a Russian institute for genetic research.

Visitors flock to see this church tower's unintended feature: It happens to resemble a giant chicken from multiple points of view.

The abandoned "Red Star Train Graveyard" is the final rusting place for precious artifacts of train history.

Lima’s Museum of Anthropology is lined with thousands of elongated human craniums.

The world's largest squirrel statue clutches a pecan bigger than your head.

The ruins of a cotton mill that was burned in the Civil War are still hidden in a Georgia forest.

Visit this playground of waterfalls, caves and sinkholes.

Crumbling ruins mark the site of a couple's grisly murder in the woods.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

A wealth of local folk art, antiques, and curios, without ever leaving your car.

The Ozarks' strangest dwelling.

Where hills of dirt conceal the burial ground of one of the most powerful ancient Native American societies.

Twenty-year effort to raise a castle using tools and techniques from the 13th century is now abandoned in the Arkansas woods.