This off-the-beaten-path abandoned town is a relic of Montana's silver mining boom.

New fungal and bacterial species call this deadly lake home.

This amazingly preserved Gold Rush town is a historian's dream.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

Hundreds of drawings left by the land's previous inhabitants remain mysterious.

This old train trestle and collapsed tunnel once allowed the railroad to negotiate the steep slopes of the Colorado Rockies.

Once a lonely sentinel on the edge of the Great Plains, this rebuilt trading fort offers a glimpse of life on the Santa Fe Trail.

The remains of a World War II-era Japanese American internment camp dot a windswept Colorado hill.

The site where a nuclear bomb was lowered over 8,000 feet underground and detonated as an experiment in natural gas extraction.

The remains of the dam that unleashed a 15-foot wall of water on Denver.

Once an unstoppable source of gold and silver, this town came to a grinding stop when the groundwater proved deadly.

The scene of one of the darkest moments in American labor history has been left essentially untouched since the tragedy.

Kentucky, Tennessee, and Virginia meet at this point in the Cumberland Gap.

Charleston's historic city jail once held everyone from pirates to Civil War POWs.

These mysterious ruins are hidden amid this sleepy coastal city.

The only road through the heart of Glacier National Park.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

The final resting place of a space program monolith.

Not merely a museum – but a whirring powerhouse that offers a subterranean peek into the heart and soul of cable car operations.

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."

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

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

The seawater playground of gilded-era San Francisco burned to the ground in 1966.