This massive complex is made up of hundreds of smaller temples that date back to the ninth century.

The oldest stone house in Paris was built by its most famous alchemist.

Now home to a drinking establishment, this building has a macabre history.

The first steel dam in the world and the only one still functional in the United States.

This unique formation is characterized by hexagonal basalt rocks stacked in unique formations.

California's first suspension bridge.

A picturesque example of brute-force engineering conquering nature.

A breathtaking 19th-century trail overlooks Lake Tahoe.

Many generations of travelers have passed through the steep, smooth walls of this canyon.

Once the largest town in eastern Yuba County now sits abandoned.

Although now a decaying ruin, this stone cabin's history includes several notable figures.

A working cattle ranch with remarkably well-preserved prehistoric petroglyphs and ancient ruins.

Hidden in the Chihuahuan Desert resides an amazing collection of petroglyphs.

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

This dry lake bed contains the oldest known petroglyphs in North America.

One of the world’s largest collections of petroglyphs records 2,000 years of human activity.

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

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

Mysterious ancient boulder carved with petroglyphs in the mountains of Western North Carolina.

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

A coastal rock outcrop with mysterious inscriptions variously attributed to Native Americans, Portuguese, Phoenicians, Norse, and more.

This mysterious petroglyph evokes the ancient swastika symbol but was later vandalized with the more troublesome Nazi one.

Neither Spanish settlers nor anyone since has been able to tell who built these strange California rock walls.

An architectural gem nestled into a promontory overlooking a prehistoric landscape.