Old Danish castle immortalized in Shakespeare's Hamlet.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Copenhagen's celebrated theme park and gardens.

Seat of the Duke and Duchess of Devonshire for centuries.

This bridge is the first to be made entirely from iron, but designed like it was still made of wood.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

Hear the quietest sound from across the dome.

It would be a crime to miss it.

This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.

An old-timey wax exhibition campily depicting New Orleans legends and scandals.

The oldest cemetery in New Orleans, resting peacefully for over 200 years now.

The final resting place of American icon Buffalo Bill, and a museum that aids in telling his tale.

These aggressively sustainable art homes look like something out of 1970's science fiction.

This southwest-styled home in Santa Fe claims to be the oldest house in America thanks to an ancient bit of foundation.

This innocuous New Mexico storefront was once the secret jump-off spot for Manhattan Project scientists.

See massive fossils that are over 200 million years old in northeastern Arizona.

Sleep where gangsters fell amidst smoke and flame, with nary a bullethole to show for the legendary struggle.

An urban laboratory.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Experience a charming 1930s version of "infotainment."

Don't blink or you'll miss it.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

The world’s largest concentrated solar plant generates as many problems as megawatts.

Thousands of turbines whir at the origin of North American wind power.