Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

The first Russian Orthodox church in North America and an Alaskan landmark.

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

The only road through the heart of Glacier National Park.

This tiny square mile of Canadian sand was once considered the world's smallest desert.

An abandoned network of military bunkers and tunnels open for anyone willing to descend into the darkness.

New Plymouth, Idaho is the only U-shaped town in the United States.

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

The rusting remains of the largest assembled WWII fleet on the West Coast.

The former Naval shipyard is open for exploring - mostly.

This infamous prison has a store where you can buy goods crafted by incarcerated people.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

A man-made island in scenic San Francisco Bay.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

San Francisco's newly reopened hands-on science museum.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

Not truly a ship nor a building, the Navy's first and last "landship" is now abandoned due to clerical issues.

An urban laboratory.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Ancient pueblos built into the base of a natural canyon wall.