The best preserved Paleochristian basilica in Rome hides a number of oddities and secrets.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

An Italian ghost town that fought obscurity, until a mysterious illness brought it to its knees.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

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

A Nesting Doll of Churches.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

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

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

World's largest collection of serial killer artwork and other macabre exhibits.

Legend has it that any woman who kissed this statue would soon be married.

The roof of this ancient mausoleum is made from a single Istrian stone weighing a massive 230 tons.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

Psychoanalyst Carl Jung reported a paranormal experience after visiting this mosaic-lined Roman baptistry.

An incredible mosaic-lined monument said to have held the remains of an ancient Roman empress.

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

An island on the Venetian Lagoon hosts this stone chair that has nothing to do with the King of the Huns.

The pile of books behind the dignified writer gave the statue a most undignified nickname.

In the past, Renaissance sex workers were encouraged to entice customers on this bridge.