This one-time health resort was used by aristocrats around the world.

An ancient neolithic tomb that only sees the sun twice a year.

This rustic cabin, outfitted with gun slits, was once home to John D. Tewksbury, patriarch of the bloodiest family feud in American history.

An explosion of natural color known as "the river that ran away from paradise."

No one's quite sure why there's a metal megaphone bolted on two rocks in the middle of the Mojave Desert.

This crumbling folly looks like an enchanted left over from Middle Earth.

A walkable map of the world, made from soil and stone by one man.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

Watch the newest land on the planet form before your eyes.

This erect, phallic geological spire wasn't always named so domestically.

This "preacher's pulpit" once used for pagan ritual, is home to a new, and dangerous ritual.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

A remarkably intact castle that once was the largest in Ireland.

The former hotel where Tesla invented the radio.

The ruins of an 11th-century Norman castle with a rare, perfectly circular shape.

A Mars simulation in the southern Utah desert.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

More than half of this Indian palace is drowned but it looks all the more spectacular for it.

The lighthouse central to the 1980s horror classic "The Fog" is, in fact, located in one of the foggiest areas of the Pacific Coast.

Mine your own precious stones.

Obelisks and stone pineapples in the Irish countryside.

One of the world's largest telescopes, stares into the night sky with two huge mirrors.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.