Macabre astrological automaton clock dating to the late 1400s.

The world's second-largest sundial, made entirely out of stone.

Once one of the largest producers of pig iron in the world.

A 56-foot tall statue of the god of fire looks out over Birmingham, Alabama.

Every last book in this bookstore is signed by the author.

A sacred site for Native Americans surveyed by George Washington and owned by both King George III and Thomas Jefferson.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

Home to the deepest rift anywhere on Earth.

Dramatic river bend surrounds a natural red-rocked pedestal.

The cinder cone volcano with a less than complimentary name.

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

A cave's rare beauty held a cavernous secret hidden underground.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

Wee (and not so wee) footprints that insects and reptiles of the Paleozoic Era left behind.

Museum on earth sciences featuring a recreation of a famous curiosity cabinet.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.