Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The secluded site of a 1943 plane crash and amazing rescue is only accessible by hiking through the woods.

These constructed wetlands naturally filter millions of gallons of treated wastewater every day.

The highway's southernmost spot is a beloved local attraction.

The smallest post office in the United States is no bigger than a broom closet.

A building so large that it has its own weather.

Island ghost town detailing Flagler's folly in building the Overseas Railroad.

A monument celebrating the idea of reaching inaccessible places.

12,000 sq. ft. museum tracing erotic art from antiquity to modern times.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

The interior of the Overlook Hotel in "The Shining" was based on this Yosemite original.

A glimpse into the lives of the the Miwok and Paiute people in Yosemite National Park.

Concrete strongholds stand guard over the Golden Gate.

This grinning pup statue is all that's left of what was once a ubiquitous Bay Area diner chain.

Guns that have been defending San Francisco since 1904.

A man-made island in scenic San Francisco Bay.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

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

Staircase winds down the side of Telegraph Hill through gardens, wild parrots flying overhead.

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

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

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

Frank Lloyd Wright died a year before construction on his largest public project even began.