A fire lookout atop a glacial pinnacle is reached by climbing three vertiginous flights of stairs.

The only remaining arch of the oldest stone bridge in Rome stands in the middle of the Tiber.

For nearly 50 years this airplane that crashed during World War II remained missing in the remote Australian backcountry.

The second-longest continuous wall on the planet protects a hidden secret in the deserts of India.

This museum showcases the history and contributions of the U.S. Army to the medical industry, both on the battlefield and off.

Roman-era ships unearthed...

This state park was once an important Native American cermonial center.

Burial mounds of prehistoric Native Americans who lived along the DuPage River.

Where hills of dirt conceal the burial ground of one of the most powerful ancient Native American societies.

Over a dozen Native American earth mounds dating back over 2,000 years dot this Tennessee archaeological park.

These ancient ritual mounds are our best window into the culture of the ancient Mississippians.

Native American burial mounds? Giant gopher dens? No one knows what created the Mima Mounds.

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

Wandering this ancient burial place offers a glimpse of the afterlife in the fresco-adorned tombs of an ancient Etruscan civilization.

A ruined Maya city that suffered a years-long case of mistaken identity.