Native Americans built this circle of stones, which was used to predict astronomical events.

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

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

The first declared National Monument in the United States.

Near-constant high winds deform the trees on Spruce Knob, the highest point in West Virginia.

A particularly creepy abandoned hospital that sparks interest for lovers of the supernatural.

These free-roaming horses were once destined to disappear from the land.

A geological mystery on Camelback Mountain.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

A spiritual vortex among the red rocks in Sedona.

A former mental hospital founded in the 1930s by a eugenicist who advocated for the forced sterilization of patients.

Exact replica of the ancient monument, but much, much lighter.

Outsider art meets paleontology at this roadside reptile repository.

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

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Rumor has it the hot dog stand was targeted by two Russian nuclear missiles.

This sprawling farm was once a Cold War-era hideaway for the nation's top diplomats.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

The hide of Stonewall Jackson's equine sidekick is on display not far from where the ashes of his bones are buried.

A former major munitions plant that has been converted into a sprawling art space.

An enormous warehouse filled with parade floats collected from over 50 years of patriotic celebrations.

Lines from a walking song are etched into a rock in Natural Bridge State Park.

One of the last active volcanoes on the Eastern seaboard.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.