A geological bull's-eye visible from outer space.

Climb atop one of the world's longest and heaviest trains for an unbelievable journey across the Sahara Desert.

A speakeasy takes on Chicago's drinking culture.

Hot Doug's "Hot Dog" Stand.

A century-old network of freight tunnels underneath the city's historic business district.

Rivers of cattle blood gone, a strange Escheresque building remains, the last of its kind.

The world's first hotel built in an abandoned water-filled quarry.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

This abandoned, turn-of-the-century astronomy hub is now the subject of more photographs than it ever took.

This abandoned mansion has a window for every day of the year, and is a temple for ghost hunters.

This Arabesque Italian castle was built with a primitive, if ingenious, air-conditioning system.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

Erotic art covers the walls of the largest ancient pleasure palace.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

Pompeii's less famous neighbor is still revealing her secrets.

Thirty creepy ghosts now inhabit this decaying 14th-century church.

A submerged village appears when dam levels drop.

A micro-communist utopia in Spain with no police, no mortgages and full employment.

An abandoned airport in the middle of nowhere.

Berlin's old airport.

Remnants of an exploded schooner and wrecked submarines form a breakwater.

A narrow passage next to a cafe leads to a courtyard exploding with murals, tags, and paste-ups.