This spectacular track has run continuously since 1882.

The often-overlooked ruins of one of the first buildings designed by famous landscape architect Frederick Olmsted.

The longest continuous lava tube in Oregon.

A 120-year-old legend concerning an empty circular patch in the North Carolina woods.

The artist James Turrell is repurposing an extinct volcano crater as an observatory to experience the cosmos.

In the remote high desert of New Mexico, a strange array of poles beckon fury from above.

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

An obscure waterfall that looks like something out of a fantasy novel.

California's own medieval Italian castle, authentic down to the 300-year-old iron maiden in the dungeon.

San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

The Magical World of George Phar Legler.

Ruins of a Carnegie family mansion on Cumberland Island.

Bad farming practices caused this unnatural natural wonder.

America's only nuclear missile silo open to the public.

The Grand Canyon of Texas.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

Even Henry David Thoreau found this glacial pothole irresistible.

The crumbling remains of a 19th century fortess.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

This bridge is haunted by the ghost of a distraught mother.

Half of a waterfall goes into the river while the other half seems to disappear.

They call this long foot bridge a swinging bridge, but really it's the bouncing you have to watch out for.

This narrow canyon has been carved by the river over thousands of years into spectacular and curious forms.

This naturally heated mountainous creek has created a group of neon blue pools of potentially deadly boiling water.