This stop on the Camino de Santiago stands high above the underwater ruins of a medieval town.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

Plaques on its facade commemorate the Tiber's most destructive deluges.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

This basilica is dedicated to two saints, one of which is known more for his famous quote.

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

Genesis of modern hydroelectric power.

Mysterious 500-year-old tapestries depict a unicorn hunt.

The home of the first American-born saint is one of the only curved buildings in New York.

Wall Street has a new heroine, a bronze statue of a small but fierce girl.

This hidden oasis features a stunning view of the Hudson River and the Palisades from a castle-like museum.

Nassau Hall has served as army barracks, a museum, and played a key role in the American Revolution.

The final resting place of many of New Jersey's most famous residents, including U.S. history's most in-vogue antagonist, Aaron Burr.

The United States’s oldest funicular railway glides up and down a steep Pittsburgh street.

This extraordinary Depression-era expenditure was modeled after a postcard of a Mediterranean hotel.

A dramatic, 360-degree recreation of Pickett's Charge in the Civil War.

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

A bizarre roadside attraction and the first instance of miniature golf in the world.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

Mile-long cave system near Great Smoky Mountains.

A recreation of the doomed ocean liner in the middle of the Smoky Mountains.

Knoxville’s architectural icon was the symbol of the 1982 World’s Fair, even catching the googly eye of Bart Simpson.