A total of 999 stairs lead visitors through a massive hole in a mountain known as the Gateway to Heaven.

European castle ruins in an American state park are actually the product of death and grief.

Discover diverse aquatic life and befriend resident turtles at this private diving grotto in north Florida.

This restaurant serves wood-fired fare served in a natural cave with a live spring.

The "worst battleship ever built" is enjoying a grand second act, submerged 30 feet in the Gulf of Mexico.

A historic, scenic mill that was forced to close due to overlogging.

The seventh largest spring in the world.

Before becoming a public park, this spot was a shell midden, a fort, and an amusement park.

A local landmark with generations of spraypainted messages, and more being added each day.

A historic landmark and museum filled with curious objects representing the history of Key West.

The highway's southernmost spot is a beloved local attraction.

The museum chronicling a treasure hunter's dream, fulfilled.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

The world-record holder for the longest bridge stretching continuously over water.

"We Seceded Where Others Failed."

One of the oldest living oak trees in the Southeast.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

The walls of America's oldest masonry fort famously "swallowed" cannonballs.

Must form and function forever remain at odds? Not if the Florida Department of Transportation has its way.

This iron and wood Civil War city-ship was the first vessel to be sunk by an electrically detonated torpedo.

This collection of Wild West movie memorabilia also claims to hold some secrets of the Lost Dutchman's mine.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

Pensacola's UFO home has withstood many hurricanes—just as the experimental 1960s design intended.