This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

An original apothecary from 1792.

This ancient Spanish castle sits high upon a hilltop.

Mine shafts and hard pastries await visitors at this massive mountain of salt.

The 28,000-year-old specimen is remarkably intact.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

The prototype for all Nazi concentration camps.

The only road through the heart of Glacier National Park.

A former department store turned into a quirky restaurant.

Come for the pizza, stay for a performance on the world's largest theater pipe organ.

After a short-lived attempt to bring America in line with the rest of the world, this road was left in metric.

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

A geological mystery on Camelback Mountain.

This public square capitalized on a single Eagles reference to bring some life back to an Arizona town.

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.

The world's largest rose bush has literally outgrown the pioneer museum it was planted behind.

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

Limestone caves with spectacular showcase chambers.

A spiritual vortex among the red rocks in Sedona.

This historic national park is covered in the stunning ruins of red rock pueblos.

Eons ago, a rushing lava river formed this pristine passage through solid rock.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."