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

In 1975, a forestry worker in Arizona claimed to have been abducted by a UFO.

Colorful sand dunes create a unique attraction in this part of Utah's red-rock country.

Nature has shaped this drainage tunnel into the digestive tract of a mighty beast.

Known as the most dangerous bridge in the world, the Hussaini Hanging Bridge is only one of many precarious rope bridges in Northern Pakistan.

In 2018, Pohoiki Road was severed by lava flowing from the eruption of Kilauea.

This sandstone gorge in New York State's Adirondack Mountains is home to waterfalls, flumes, and more.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

The perfectly named cave drop is the deepest in the continental United States, almost matching the height of Seattle’s Space Needle.

Formerly known as National D-Day Museum, this collection commemorates the battles of Normandy and WWII.

In Rickwood Caverns, visitors can travel hundreds of feet underground and see beautiful formations unique to the region.

Since it formed millions of years ago, this cave system has been a sacred burial ground, a Prohibition-era speakeasy, and the center of an amusement park.

Orr Park's dead trees have been carved into a menagerie of whimsical visages.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

148 feet long and in the middle of a verdant forest.

Famous for its bio-luminescent inhabitants, known as "dismalites."

Hide from the tourist hordes in these relatively unknown, and unguarded lava caves.

One of the best places to dig—some say on the planet—for six different types of chalcedony.

Crystal hunters can dig for their own stones at this DIY mine in Arkansas’ quartz belt.

The hike to this stunning waterfall on a black sand beach is not for the faint of heart.

The world’s largest combined collection of U.S. and Russian aircraft got its start in a poultry building.

This abandoned mining village was predicted to resist decay longer than any other modern human settlement.

Two massive boulders, rocking back and forth with the ebbing of the sea.

This tombstone marks the spot where the legendary British spy met his end.