This hiking/biking/horse trail along an old railroad grade features trestles, tunnels, and a roadless stretch through the scenic Susan River canyon.

An abandoned mine where dreams of quicksilver trickled away over 75 years ago.

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

This sinkhole in the Arizona desert is filled with carbonated, arsenic-rich water

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

See massive fossils that are over 200 million years old in northeastern Arizona.

Some 10,000 works of ancient rock art cover these volcanic basalt outcrops near the Gila River.

This oasis-like spring in the Sonoran Desert is home to unique, endangered species.

A strenuous, unofficial trail leads to spectacular views in one of America's most remote national monuments.

America's only nuclear missile silo open to the public.

After a short-lived attempt to bring America in line with the rest of the world, this road was left in metric.

This giant steer-skull edifice refuses to die.

Legend says train robbers stashed their gold within the depths of this unusual cave.

Limestone caves with spectacular showcase chambers.

The world's largest rose bush has literally outgrown the pioneer museum it was planted behind.

A wild west cemetery in Tombstone, Arizona, provides a window into the Old West.

A living snapshot of a different time in America is preserved and maintained by a community of volunteers.

A museum dedicated to the alleged Roswell Incident.

This fast-food outlet is the only space and UFO-themed McDonalds in the world.

This is one really big nut.

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

The state bird of New Mexico, constructed entirely out of garbage.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.