Rippling sand dunes frozen in the Arizona rock.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A terrific purveyor of natural history objects and curios.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

A huge musical instrument played by the ocean.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

Incredible miniature towns and buildings created and decorated with thousands of tiny rocks.

The mysterious 855-foot zigzagging stone wall has been baffling people for centuries.

The site of the Scopes Trial contains a small exhibit dedicated to the famous case.

This stone incorrectly marks the 35th parallel, causing some territorial kerfuffles.

A floating museum that was sunk by a flood and left to rot in the tides.

A late sculptor's last project was to turn this abandoned cement factory into a castle-themed amusement park.

One of the world's earliest skyscrapers.

One man's unrequited love stands in a glass box forever.

This spot in St. Louis, marked with a simple sign, has seen more pro baseball than just about anywhere else in the world.

This titanic oil company sign is a reminder of the Americana boom of the 1970s and also its commoditization.

One of few surviving standpipe water towers in the U.S.

What was meant to be a temporary exhibit is now a permanent fixture at the St. Louis Zoo filled with beautiful birds.

An abandoned factory along the Mississippi coated by a giant mural.