A burnt orange monolithic dome structure perched on a hillside near Interstate 280.

A little-known subterranean street runs under some of the best-known buildings in Chicago's River North.

The iconic Chicago sculpture hides a beautiful and easily overlooked plaque on the backside.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

The graffiti-covered remnants of a former triangulation station are balanced precariously on this California peak.

A large instrument played by the wind.

These decaying bridges 1,000 feet high are a reminder of the skill it took to cross the Colorado Rockies by rail.

The remnants of the base where US Army troops learned how to fight in extreme conditions.

A wall of chewing gum moonlights as collective art.

The tech giant built three enormous glass orbs in Seattle so employees could work inside a rainforest greenhouse.

Birdhouses, peacocks, animal sculptures, and a graveyard are all found along this eclectic nature trail.

Rare and gorgeous birds abound in this protected wildlife sanctuary.

A modest reminder of treacherous waters at the Golden Gate.

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

The second building of its name to occupy this location might be the finest flatiron building in San Francisco.

These WWII-era murals were initially booed as a libelous portrayal of the American dream but have survived multiple attempts to have them destroyed.

Big gun installations, built over a massive cemetery, now abandoned & hidden in trees.

Shoot for par over the bodies of the dead on this cemetery-cum-golf course.

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

Only hotel where you can legally launder money.

A sign at the end of the Santa Monica Pier marks the traditional end of the legendary American highway.

One of the first skyscrapers in Santa Monica, and a famous getaway for the Hollywood elite of then and now.

Dubbed the "Blade Runner dragon," this buzzing neon sign is a beloved local icon.

The magic's in the hole!