During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

A painfully obvious spy house sits right across the street from the Russian Embassy.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Home to items never before seen by the public.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

The site of the gruesome massacre—and maybe cannibalism—of five men, a tragedy that made Alferd Packer infamous.

Inside this shop, visitors are treated to a unique blend of natural history and art.

This nearly abandoned town was once a thriving mining community until a series of fires.

This National Natural Landmark is one of the best examples of a “mass wasting” in the world.

Historic, 19th-century wagon wheel ruts cut into soft volcanic ash.

Birds with backpacks expedite film development for a rafting company on a remote Colorado river.

Open-air cremations in Colorado's self-proclaimed spiritual mecca.

A coal fire has been burning underground here since 1896.

Toss a Frisbee through the ruins of this Colorado gold mining town.

Unlike most arches, this geological oddity formed in a volcanic dike.

There are eight natural springs around town, each with a slightly different taste.

This grand stone tower was dedicated to a famed American humorist almost by coincidence.

Climb to the top of this spiritual tower, and you'll be rewarded with spectacular views.

This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.

This interpretive path lets you get up close and personal with dinosaur bones.

In the middle of a suburban Denver neighborhood is a cave that once provided solace for a prominent Ute chief and his family.

The largest dinosaur trackway in North America is tucked away among this canyon's ghosts and archaeological gems.