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

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

World's first "penitentiary," meant to be humane, drove men insane.

Mountain known by the Tillamook Tribe as "the place of the supreme deity."

A grave surprise in the downtown area of New England's second-largest city.

At 135 years old and counting, this historic print shop is heaven for poster nerds and music buffs.

Mile-long cave system near Great Smoky Mountains.

New Orleans' famous cemetery, located on the site of a former race track.

This historic "City of the Dead" lies prominently in the center of New Orleans' famous Garden District.

The trials and tribulations of marking Poe's grave.

This cemetery has graves dating back to the 17th century, including the city's oldest carved tombstone and an ominous cryptogram.

The world's longest known cave system.

The largest earthwork effigy in the world.

The magic's in the hole!

A beautiful Victorian-era cemetery, complete with a miniature village.

The last of its kind in the country.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

A heavenly experience, right here on Terra Firma.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

Four glass boxes hover over 1,000 feet in the air to give visitors an unparalleled view of Chicago.

The haunting "Hell House Altar" is one of the few remnants of an abandoned college that has been a magnet for local legends.

A beautiful geyser under environmental threat.

The oldest cemetery in New Orleans, resting peacefully for over 200 years now.