The prototype for all Nazi concentration camps.

The site of Austria's biggest concentration camp now honors its victims.

The memorial stands at the intersection of the rivers Morava and Danube.

A rebuilt Roman city that was once the largest Roman settlement in the region.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

A backdoor to Machu Picchu that only the most foolhardy infiltrator would attempt to breach.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

Did Inca children also slide down these smooth rocky slopes above Cusco?

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

A wonderful display of arts and crafts handmade by local artisans in the Southern Appalachians.

This winding road of 318 curves is a must-visit for (careful) motorcycle and sports car enthusiasts.

This road in the Great Smoky Mountains was supposed to assuage a displaced community, but ended up a $52 million dead end.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

You can find America's highest suspension footbridge at Grandfather Mountain in North Carolina.

A 315-foot spire jutting out from the Blue Ridge Mountains makes for breathtaking views.

The scene of the largest surrender of Confederate troops at the end of the American Civil War.

This hollow steel globe is the second-largest in the world.

I-95's Tijuana-style celebration of kitsch at the Carolina border.

A statue honoring 44 continuous years of greeting passing ships.

From failed port town to Civil War fort, the ruins of this former defense saw their finest day in the television age.