A beautiful geyser under environmental threat.

An architect's childhood fantasy treehouse made real.

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

The first declared National Monument in the United States.

When ecosystems collide in the arid Southwest.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

A place where the laws of nature seem to have gone completely berserk... but of course haven't.

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

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

A fitting attraction for the corn capital of the world.

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

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

These pretty kitties killed and ate as many as 135 railway workers.

Every day a troupe of pampered water fowl walk the red carpet to their favorite fountain.

Walk the whole Mississippi River!

Erosion and time have created a naturally-formed water park.

Giant granite rocks standing end-to-end like a train of circus elephants.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

A mythical bird etched into the face of a rock doubles as the mascot for a nearby school.

Quirky water tower advertises the long-gone Brooks Tomato Products Co.

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

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.