An acoustic anomaly with a mysterious cause.

A recreated Stonehenge stands in a country field, complete with Easter Island moai heads standing as sentries.

Scale replica of China's ancient terracotta tomb warriors and Forbidden City are the side project of an eccentric millionaire.

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

A white oak with property rights.

Display that gathers the basic elements of the universe in one convenient location.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

Mysterious ancient boulder carved with petroglyphs in the mountains of Western North Carolina.

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

Moonbows over Kentucky.

Live long and prosper in Tennessee.

This structure among the trees was the result of divine inspiration.

The world's longest known cave system.

This replica of the Greek structure is in the heart of Nashville.

Giant instrument-shaped home in Fayetteville, Georgia.

One of the deepest blue holes in the world.

One of the oldest living oak trees in the Southeast.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

A real (but thankfully not live) missile stands tall as a monument to the United States military in the small town of Cordele.

Fire meets ice at the southernmost volcano on Earth.

Natural time capsule containing an alien ecosystem.

Half of a waterfall goes into the river while the other half seems to disappear.

Bohol's mysterious brown hills.

Ethiopia's "smoking mountain" is in one of the hottest regions on the planet and is home to two lava lakes.