It took years to decode its mysterious messages.

The largest permanent Monopoly board makes one of the longest games even bigger.

A giant chess set, minus the psychedelic drug trip.

This unique formation appears as though an asteroid landed on the forest.

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

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

A vast city of the dead, where the deceased outnumber the living by more than a million.

The most beautiful Taco Bell in the world even has surfboard parking.

Radioactivity still cause for concern at this urban explorer's paradise.

This controversial depiction of the "Founder of California" looks as though it was sculpted from mashed potatoes.

Frank Lloyd Wright died a year before construction on his largest public project even began.

This abandoned boat was left in place thanks to its rotting beauty.

'Cause the fence start shaking, the earth was quaking.

Built by the inventor of the radio, this abandoned hotel has housed early radio employees, military men, and a dangerous cult.

A huge work of Burning Man-inspired outsider art on the grounds of a California winery.

Massive prehistoric mammals used these stones as oversized scratching posts.

A poignant memorial to a young boy whose death spurred a dramatic increase in organ donations in Italy—dubbed the "Nicholas Effect."

This massive redwood tree has a hole in the base big enough to drive through.

An optical illusion found amid a logged redwood forest.

A trash dump made beautiful by nature's power.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

Monumental sculptures of Patrick Amiot, constructed from debris, detritus, and determination.

A tribute to the life and work of the beloved "Peanuts" cartoonist.