This massive subterranean fissure is known as the "underground Grand Canyon."

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

This abandoned Slovenian military barracks has become a punky-political art squat.

This restored Portuguese cafe may well be the most beautiful place in the world to grab a Big Mac.

A hidden three-foot-wide house separates these two regal churches.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

Elaborate tile work in this railway station tells the story of Portugal.

A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

The last bastion of Roman presence north of the Alps looms over a German town.

An ornate sculpture of an ox in repose marks the former entrance to Nuremberg's medieval meat market, which was destroyed during World War II.

This statue includes the molehill that toppled a king.

Three hundred years of preserved Spanish colonial history in San Antonio.

An ivy-covered arch bridge dedicated to Tejano music singer and legend Rosita Fernandez.

Officially named the "Loneliest Road in America," this barren stretch of Nevada road offers almost nothing but sky and open fields.

The fifth-longest natural arch in the world, and the longest outside China.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

A natural formation that resembles a camel resting in the New Mexico desert.

The oldest continuously occupied public building in the United States.

The highest point in Oklahoma used to be a lawless outlaw's paradise.

This church was transported brick by brick from the ruins of a 16th-century city into Panama City's current historic district.

A series of waterfalls so massive they straddle the border of Argentina and Brazil.

Of the many Jesuit missions in South America, this complex is one of the best preserved.

This massive Brazilian church is built like an angular, technicolor pyramid left by Mayans from the future.