Parking garage where Bob Woodward met Watergate source "Deep Throat."

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

At this Minnesota state park you can easily wade across the source of the mighty Mississippi.

A larger-than-life statue of America's favorite sundae marks the place it was invented.

Overgrown ruins of a turn of the century island fort that sees very few visitors.

Singing sand that stands as the final remains of an ancient lake.

Captain John Smith thought these cliffs were amazing in 1608 but sharks thought so 20 million years before him.

Natural catch-basin rocks covered in thousands of drawings spanning many millennia.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

This erect, phallic geological spire wasn't always named so domestically.

A nude beach alongside a washed-out road.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

The heroic sled dog of the 1925 serum run is preserved in taxidermy.

A peaceful, unique botanical garden complete with waterfalls, mini islands, and swans.

Watch the newest land on the planet form before your eyes.

Display that gathers the basic elements of the universe in one convenient location.

The fifth-longest natural arch in the world, and the longest outside China.

These black pillars of volcanic basalt seem to call mountain climbers with an unbreakable siren song.

The ravine where Jesse James supposedly performed an impossible jump to evade capture.

This massive geographical sculpture is so subtle, it's possible to pass by it without noticing.

An odd, ancient window that may have once been part of a brutal prison is embedded in the side of New York's Police Plaza.

The highest point in Arizona is an oddly snow-topped peak within the otherwise arid state.

Gorgeous cave resemble a winter wonderland.