The small cave that housed Tennessee's "first citizen."

The first full-scale tunnel built in America is short but scenic.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

Visit this playground of waterfalls, caves and sinkholes.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

Enormous lake at the bottom of a unique cave system.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

Whimsical bronze sculptures of smiling coins and houses await visitors to this park.

A dramatically eroding canyon thousands of miles from the desert.

The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

Walk through row upon row of manicured miniature trees at the United States' largest bonsai nursery.

A preserved stretch of ancient fossilized trees with an impressive gem collection to boot.

An eerie and beautiful group of columns mark the site of a grand mansion lost to time and fire.

Built following the War of 1812, this fort has withstood hurricanes for centuries.

These steeply terraced ruins are a stop along the Inca Trail to Machu Picchu.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

The remains of what was the most important religious complex in coastal Peru for over a millennium.

Now containing the bones of the actual conquistador, instead of someone else.

The mortal remains of an estimated 70,000 people lie in the basement of a monastery in Lima, Peru.

Tucked behind the Institute of Neurological Science down a decrepit street resides the largest display of human brains in Latin America.

A remarkable geological formation resembling a forest made of stone.

This scalding hot river was thought to be a myth until one geoscientist made it his quest to study the mystical waters.

A mysterious pre-Incan ruin believed to have miraculous healing powers.

The highest tropical mountain range in the world is in Central Peru, home to a vast array of exotic and quirky plants and animals.