An inconspicuous footbridge beloved by San Diego locals.

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

This semi-hidden Manhattan restaurant is based out of a loading dock.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

"Dark Sky Park" is heaven on Earth for astronomers, one of the rare U.S. locations with no artificial light pollution.

An organ located deep within a cave, whose "pipes" are the geological features of the cave itself.

Half of a waterfall goes into the river while the other half seems to disappear.

The highest bridge in America was built for an almost unnervingly small amount of money.

A meditative space out of a fantasy story.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

When ecosystems collide in the arid Southwest.

Town of spiritualists and mediums in Florida.

The longest navigable underground river in the United States is home to countless blind and albino animals.

Imagine playing a version of Legends of the Hidden Temple, but with a distinctly Southern Gothic flare.

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

A museum dedicated to exhibiting remarkable outsider art.

This naturally heated mountainous creek has created a group of neon blue pools of potentially deadly boiling water.

Tour the world's largest deep-hole dimension granite quarry, where you can view the plant where gravestones are made and roll a ball down the outdoor granite bowling alley.

One of the oldest living oak trees in the Southeast.

Huge masonic hall in Philadelphia with lavishly themed rooms.

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

These aggressively sustainable art homes look like something out of 1970's science fiction.

A popular European tradition makes its way to the states on one of America's most famous bridges.

The abandoned personal amusement park of the King of Pop.