The source of America's longest river is also a historical landmark and the start of a famous nude run.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Dig for your own trilobites in this goldmine of invertebrates.

The only road through the heart of Glacier National Park.

Stroll through a wonderland of stupendous moss-covered trees.

Secret gardens just a few miles from downtown Atlanta.

This naturally-sourced hot spring is now home to a clothing-optional resort.

Community owned and operated, this property is home to a diverse set of nudists.

Discover for yourself what Herb Caen referred to as "the best kept secret in the Bay Area."

Rare and gorgeous birds abound in this protected wildlife sanctuary.

The Hudson River School comes alive at this palatial estate.

Stripes of flowers bloom each spring in a 50 acre rainbow of color.

This woodland architectural installation acts as a camera obscura for the heavens.

California's own majestic geyser is powered by a subterranean volcano.

A miraculous natural phenomenon known as "the spring that breathes."

Earth's tallest volcano is sacred to Native Hawaiians, and home to a dozen world-class observatories.

One man has installed bathtubs into the Utah desert floor to harness the powers of a natural hot spring.

A natural rock formation believed to be a cure-all.

The only working large-scale tea plantation in the United States.

The abandoned ruins of America's first private zoo are open for exploration in the Catskills.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

This rare example of a "tidefall" is a spectacular drop from the cliffs down onto the beach.

Gnarled canopies of pink and purple wildflowers arch over the trail to the summit.

A futuristic climate change study is nestled deep within this public land.