The world's most active stratovolcano is almost always erupting.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

Pilgrimage site for star-crossed lovers.

Jesus' footprints and the first catacombs in the world.

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

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

2300-year-old Roman road connecting the empire.

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

Museum dedicated to the terror regimes of Hungary.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

Look closely and you’ll notice that the color changes a third of the way up the tower.

Home to a vast and influential collection of Shakespeareana.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The walls of the iconic dome are hollow and have a secret stairway.

Home to items never before seen by the public.

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

This elaborate towering structure was once famed for its revolutionary height.

Ant sculptures march up the side of what used to be an iconic spot in punk rock lore.

Yo, Adrian!

The first American department store, and home to the largest operating musical instrument in the world.