Crystal clear lake with a shoreline of travertine located in a Colorado canyon.

The world's largest key collection features keys to the White House, Frankenstein's castle, and Hitler's bunker.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

Carved faces add a touch of magic to this island's impressive oak trees.

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

The show's fictional Korean medical camp was created in the Santa Monica hills.

A tiny red pebble marks what may be the quietest outdoor spot in the United States.

This Asheville chair museum wants to revive a dying art.

The oldest operating cemetery in Denver is the eternal home of some of the Centennial State's most famous residents.

Where the first "expert riders, willing to risk death daily" for the Pony Express were recruited.

This 140-year-old beacon off the Florida Keys marks the wreck of a Navy ship that once roamed the Caribbean hunting pirates.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

A hands-on traveling collection of the innovative devices of yesteryear.

This wondrous waterfall rushing down a green-covered mountain wasn't discovered until 2010.

The old Route 66 town straddling Texas and New Mexico died along with the Main Street of America.

An unusually designed bridge from the 1920s was built to withstand the tides and winds of Maine.

At the center of an island in the middle of the Indian Ocean is a deep chasm ringed by tall waterfalls.

A shining, cold, black organ lies in San Francisco's financial district.

The world's largest and most outstanding marl lake regularly changes color.

A little-known hot spring haven right below the highway.

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 tiny river island switches sovereignty every six months as part of a rare, centuries-old agreement.

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

Where scientists keep miles of very valuable ice from Antarctica and Greenland from melting.