Rippling sand dunes frozen in the Arizona rock.

For divers and music lovers, the Florida Keys' Underwater Music Festival provides the best of both worlds.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

An underwater city for the dead.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

An unrecognized micronation declared by Greenpeace to protect the glaciers of Chile.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

These steeply terraced ruins are a stop along the Inca Trail to Machu Picchu.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

When you can afford only half a road, you build only half a road.

It's 2 billion years old!

The remains of the first punk club in L.A.

An abandoned underground bathroom is now a space for public art.

The rest of him lived another 61 years and was buried elsewhere.

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

Australia's largest collection of rare and bizarre insects.

Recycling meets art in this colorful barricade.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

A towering bronze statue memorializes the founding father of postwar American conservatism.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Burping, gurgling geothermal mud pots by the Salton Sea.

Eulogizing an unknown man's unusual demise.

Walk through Czech history in Prague's largest graveyard.