The fairy tale castle of the "fairy-tale king."

A church of bones, decorated with 40,000 human skeletons.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

Golden Gate Park's historic collection of plants.

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

Barely visible foundations remain where Stow Lake’s “observatory” once welcomed visitors.

This private residence was the template for one of the most beloved television homes of all time.

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

The seawater playground of gilded-era San Francisco burned to the ground in 1966.

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

Concrete strongholds stand guard over the Golden Gate.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

Huge masonic hall in Philadelphia with lavishly themed rooms.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

This elaborate towering structure was once famed for its revolutionary height.

Yo, Adrian!

World's first "penitentiary," meant to be humane, drove men insane.

This university transit system is a 1970's vision of the future.

Memorializing an American tragedy of massive proportions.

Steepest flood safety railway in the entire world.

Beyond the usual stories that attend old prisons, this one has deep bloody undercurrents.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

The only way to see Pittsburgh is from the top of this lookout point, just like the ancient members of the native peoples did.

This spot memorializes one of the greatest plays in NFL history, unless you happen to be a Raiders fan.