The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

A wall of chewing gum moonlights as collective art.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Built to house a chapter of the Knights Templar, this grandiose building is a relic of Freemasonry in Chicago a century ago.

Wisconsin's most celebrated export gets the royal treatment on I-94.

Half-sized replica of the Leaning Tower of Pisa built to honor Galileo.

A towering Art Deco movie palace made to look like a Mayan temple.

Where a brain, a beauty, a jock, a rebel, and a recluse met one Saturday and changed their lives forever.

Despite its name, this fast food museum is actually a replica of the ninth McDonald's store.

Home to the world's largest refracting telescope and the birthplace of modern astrophysics.

Its eclectic exhibits range from the world’s first motorcycle to Luke Skywalker’s Land Speeder.

At the largest railway museum in the United States, you can see everything from an early steam engine to a functioning Thomas the Tank Engine.

An antique narrow gauge railway line still running through the Colorado and New Mexico mountains.

This spectacular track has run continuously since 1882.

The last physical evidence of the Lewis and Clark trail is one of their autographs etched into this giant rock.

Over thousands of years, this slot canyon was carved out of the bed of an ancient lake.

This large cemetery is known as the museum of granite sculptures.

The sweetest graveyard in the world is filled with headstones for dearly de-pinted ice cream flavors.

This tiny patch of arid sand sits in one of the greenest states in the United States.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

Mrs. Mallard and her brood are a beloved fixture in Boston Public Garden.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

This kitsch eatery is chock-a-block with bric-a-brac.