This WWII-era military installation once held an entire city within its walls - now, its walls are falling down.

This small city where almost everyone lives in the same building can only be reached via North America's longest tunnel.

Running under an entire mountain, the longest highway tunnel in North America is kept fresh using portal fans and jet fans.

An Alaska livestock farm devotes itself to harvesting wool from creatures that once ran with mammoths and sabertooth tigers.

The ruins of a town wiped out by the second-largest earthquake in recorded history.

Siberian husky that delivered a life-saving antitoxin.

Clean, cold drinking water flows from a nondescript pipe in a roadside rock face.

Considered by many to be one of the most dangerous highways in Alaska.

During the summer, surfers in Alaska take advantage of this inlet’s unusual water patterns.

While not recognized by Guinness, this chocolate waterfall is likely to be the world's largest.

Masterful ceramic fountain and map of the Pacific Basin.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

These subterranean storage areas hold emergency water reserves.

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

The giant pair of sexy legs sticking out the window of this costume store have become its main draw.

Gold Rush-era tombstones line the park's paths.

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

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

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

Home to one of the world’s largest collections of model yachts.

The remains of a ruined mansion memorialize the 1906 earthquake.

A century and a half of research in the sciences and natural history, still going strong.

An elaborate gift from Claus Spreckels is now a piece of San Francisco history.

Over 315,000 preserved amphibians and reptiles in jars.