An immense cave that has served as an outlaw's treasure trove, an underground dance hall, a nuclear fallout shelter, and much more.

Explore the cabin where the famed abolitionist once lived and the site where he fought the Battle of Osawatomie.

Over 140 boathouses built by miners from the Soudan Iron Mine in the early 20th century overlook Stuntz Bay on Lake Vermilion.

This canyon is named for a unique geologic formation where the river vanishes underground near the mouth of the canyon and reappears farther down.

These dramatic cola-colored falls have appeared in a poem by Henry Wadsworth Longfellow and a song by Sufjan Stevens.

A wonderland of caves in eastern Iowa.

This park is home to a massive bird sanctuary.

This functioning mill was built in the 1970s using parts from several other West Virginia mills.

From a canyon-like gorge, more than 20 million gallons of water emerge every day, while a smaller spring drips down, creating the illusion of an endless, gentle waterfall.

This fallen red oak tree has been transformed into a piece of trailside art.

An impressive waterfall nestled in the cliffs of Idaho's Snake River Canyon.

Located near the U.S.-Mexico border, this park remembers the famous raid of General Francisco “Pancho” Villa and his soldiers.

People of the Plum Bayou culture built these enormous mounds over 1000 years ago.

The cliff and rock formations are made out of Sioux Quartzite.

The ruins of an open-air theater built on this Georgia island in the 1970s.

Narrow gorges and deep pools created by long-ago glaciers.

Irontown was founded in 1868, as a second attempt to mine iron from the nearby Iron Mountain.