The lecture hall where Alexander Graham Bell first demonstrated the long-distance phone call.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

The atmospheric road was never meant to be so creepy.

Those who own or stay at this 500-year-old, allegedly cursed house often meet terrible fates.

The eccentric and colorful pavilions of Tower Grove park are a beloved and overlooked symbol. 

The sound of swaying stalks in this stunning grove has been named a governmentally recognized sound.

A little sculpture with a large wardrobe.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Medicinal spa created from the mineral-rich runoff of a geothermal power plant

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

Inside this Icelandic greenhouse, geothermal energy keeps tomatoes warm and growing.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

The show pony of cave systems, Fantastic Caverns manages to live up to its name.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

A swimming hole in the historic industrial quarry that supplied the marble for the Baltimore Washington Monument.

At this former Prohibition speakeasy, electric birds signaled the arrival of hooch.

A monumental statue of RCA's mascot now sits atop a historical society roof after a life of moving around.

Baltimore's first skyscraper may be home to the inspiration behind pulp fiction's most celebrated bird.

This statue honors the author's groundbreaking family story.

According to local history, this cast-iron canine was nearly melted down for bullets during the Civil War.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

It's good luck to be mocked by this monkey.

This historic funicular system combines the old with the new while offering delightful views over the surrounding valley.