Concrete strongholds stand guard over the Golden Gate.

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

A modern mechanical planetary system, part of a 10,000 year clock.

A Roman-inspired temple once controlled half of San Francisco's waters.

Prone to disastrous fires, the city of San Francisco has the Guardian, a fireboat gifted by residents, to watch over them from the bay.

A Barbary Coast watering hole built into a Gold Rush shipwreck.

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

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

The haunting ruins of Jack London's dream house.

The largest drain hole in the world.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

Towering basalt columns, a creation of fire and ice.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

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

Shakespeare has been brought to life in this open air theater for the better part of a century.

This erect, phallic geological spire wasn't always named so domestically.

The high point on the 16th president's eponymous roadway is marked by a massive version of his head.

A century-old cabin off of Highway 30 touts an unusual construction material: dinosaur bones.

A popular rock that acted as a waymarker for American pioneers.

Officially named the "Loneliest Road in America," this barren stretch of Nevada road offers almost nothing but sky and open fields.

Two mammoth statues inspired by equally tall tales lure tourists to this roadside attraction.

This historic steamboat is scuttled just a few hundred feet from where it was built over a hundred years ago.

Small Nevada town embraced its designation as the "Armpit of America" with an Old Spice-sponsored festival.

This massive mall has hundreds of shops, an amusement park, and a history of deadly amusement attractions.