A quiet nook at the top of a little-known hilltop park named after California's first poet laureate.

This teeny-tiny park built by a San Francisco man in 1962 is mostly stairs.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

A huge musical instrument played by the ocean.

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

This mosaic-covered bar is brimming with curated curios.

A big museum full of little worlds.

An urban forest overtakes what was the greatest failure of utopic urban housing.

During the 19th-century, this park was a vital trading fort.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

This 19th century hydroelectric powerhouse was the first of its kind.

This former boomtown "island" is now submerged below Folsom Lake.

The tallest bridge in California was constructed for a project that was eventually cancelled.

The arch that celebrated the completion of the Lincoln and Victory highways.

The only surviving prototype of Buckminster Fuller's revolutionary car.

This former New Jersey bus now exists as a public art exhibit.

This beloved roadside attraction welcomes visitors with his signature neon smile.

A shady solar power system that couldn't hold up to the harsh desert conditions.

This ancient village provides insight into the complexity of the pre-Columbian Fremont Culture.

A gothic palace of endless stalagmites and pseudoscorpions waits within one of the world's most beautiful caves.

The longest living non-clonal organisms on Earth.

The current Eureka County Courthouse replaced an all-wooden structure that had previously been an ice-skating rink.

Located in the remote Monitor Valley, this travertine bowl contains a scalding pool of water.

This rest area is also home to a remarkable petroglyph site.