A volcanic tunnel illuminated by natural skylights offers a shaded respite from the desert sun.

These millipedes glow not out of attraction, but as a not-too-subtle warning.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Eons old volcanic activity created one of the most stunning rock formations in the United States.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

One of the most scenic stretches of road in America winds between some of the country's oldest trees.

Quite simply the largest tree in the world (by volume).

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

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

The remains of a historic ranch house that witnessed the Civil War battle dubbed the “Gettysburg of the West.”

The ruins of this abandoned fort now stand as a picturesque reminder of America's march West.

Some of the Old West's most notorious outlaws frequented this mining town.

In a largely deserted ghost town, a little brick building recalls its history as a gold rush hub and haven for outlaws.

One of the American Southwest's most extensive collections of Navajo rock art.

A cave's rare beauty held a cavernous secret hidden underground.

A small metropolis of Pueblo cave dwellings have been carved right into the hillside of this national monument.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

Twice a year, visitors can tour the desolate site that birthed the Atomic Age.

The old Route 66 town straddling Texas and New Mexico died along with the Main Street of America.

A multi-storied adobe complex has been inhabited for more than a thousand years.

These Pre-Columbian petroglyphs contain representations of birds, deer, hunters, and even some early Native flute players.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.