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

This lake in the Cascades lives up to its name, disappearing down a hole every spring.

Oregon's unexpected high desert, displaying layers of time in a colorful show.

Man-made geyser that rises to the exact height of the Gateway Arch.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

Who needs fancy modern water slides when this giant North Carolina rock works just as well?

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

This cave holds a surprisingly colorful variety of geological oddities.

What is the Thing?

The largest natural travertine bridge in the world is nestled in a small canyon in central Arizona.

A white oak with property rights.

An unfinished rail tunnel that has since been used to house cheese and bats.

Tour the sci-fi-esque reality of governmental disease management.

Bad farming practices caused this unnatural natural wonder.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

A monument celebrating the idea of reaching inaccessible places.

A community of collapsing homes more than a mile out from the Florida coast.

Meet manatees face-to-face at this zoo for native species.

The only swimming pool listed on the National Register of Historic Places is emptied and refilled each day with naturally filtered water.

Where monkeys run wild and the humans are caged.

An emerald-green grotto just a short trip from Austin.

One of the last free public hot springs is decorated with hippie art.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

Towering basalt columns, a creation of fire and ice.