This small turbine mill along Rocky Creek was built in 1928

An average of 33 million gallons of water pour out of the collapsed cave at the heart of this spherical spring.

A historic, scenic mill that was forced to close due to overlogging.

The largest riverfront opening cave in the Ozarks.

Curios, scientific antiques, oddities for sale.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

A graveyard of bathyspheres and diving bells paints a weirdly accurate account of ocean exploration's rickety history.

Open since 1938, this diner has kept its fountain, malt machine, and all the gum that greasers left beneath its counter.

This historic cliffside mansion uses a natural cave for air conditioning.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Rippling sand dunes frozen in the Arizona rock.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

The largest source of fossilized insects anywhere.

Most-visited and most-photographed slot canyon in the American Southwest.

Dramatic river bend surrounds a natural red-rocked pedestal.

Giant pinnacles in the sun-scorched lands of Southern Utah have been nicknamed "white ghosts."

The drama of nature in full effect in this Nevada State Park.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

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

Legends surround this jagged rock formation in the New Mexico desert.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

A museum dedicated to man's boldest venture.

In the St. Francois Mountains in the Ozarks at 1,772 feet above sea level, Taum Sauk Mountain is the highest (and possibly oldest) peak in Missouri.

On the Oregon coast there is a natural hole that seems to be draining the sea.