Longest road tunnel in the world features an air treatment plant and the illusion of daylight.

A thin pane of glass keeps visitors from sliding off this futuristic skywalk.

A natural arch offers panoramic views of Yangshuo's karst hills.

This attraction is part anthropological journey and part amusement park.

Air-raid tunnels hidden beneath this opulent hotel provided shelter and an escape route—and one of the world's longest slides.

Chevron maintains one “Standard” brand station per state so it doesn’t lose the trademark.

This historic graveyard was partially paved over to create a streetcar line.

San Diego's most historic and haunted home.

This quirky UFO-shaped curiosity is often mistaken for the airport’s control tower.

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

This trailside hut was built in the late 1930s as a memorial to a young hiker.

A statue commemorating the heroic life of a Viking postman who was the Godfather of California skiing.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Thousands of people walk over this fantastic work of art every day, but how many notice it?

Equal parts record-breaking temple to consumerism and bizarre fun park, it's more than you think it is...

Inside this shop, visitors are treated to a unique blend of natural history and art.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

This plaque marks the former home of one of the first women physicians in the Netherlands.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

A unique work of automotive art calls this shopping center home.

Tucked in the back of a flower shop, its collection details the fascinating history of the Netherlands's iconic symbol.

The last of Amsterdam's original sea level markers remaining in place.