A limestone wonderland of water and subterranean secrets.

This frequently-photographed waterfall takes only a short hike to visit.

America's smallest "national forest" has only 33 trees.

Tucked away on an empty wooded lot in suburban Oklahoma City lie the remnants of an abandoned circus camp.

An American city stranded at the tip of a Canadian peninsula where strict adherence to the "49th parallel rule" became problematic.

An ethereal glowing blue ocean cave in Croatia.

Rock-cut cave complex filled with ancient Buddhist artwork.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

A series of waterfalls and pools that flow through the 'Ohe'o Gulch and into the ocean.

On the Oregon coast there is a natural hole that seems to be draining the sea.

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

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

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

This geothermal hot spring hides beneath a slowly growing mineral dome.

Site of the greatest known waterfall that ever existed.

This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

Nuclear reactor created the plutonium used on Nagasaki.

The second tallest railway trestle bridge in America.

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

This abandoned lighthouse looks like a rusting oil rig, but has managed to survive a number of storms.

A large spinning bath of liquid mercury, used to probe the early universe.

Mysterious wreckage of a small plane has been lodged in this tree since at least 1971.

"The House That Love Built" is shying away from "The House That Ghosts Love."

A bike being "eaten" by a tree is the real Vashon legend behind popular children's book, "Red Ranger Came Calling."