St. Francesca Romana, patron saint of drivers, resides in the church she founded.

A magnificent waterfall is also home to the remains of a Roman hydraulic engineering system.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

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

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

One of the most important yet well-hidden museums dedicated to the history of medicine.

The Pope’s secret escape route.

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

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

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

The underground sanctuary of a mysterious ancient cult.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

An alchemist's "magic door" stands in the middle of a Roman park.

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

The largest medical and anatomical collection in France lies hidden from the public.

The site where two doves fell in love.

The macabre collection of Jacques Sirgent, an expert scholar on the undead and all of their trappings.

The tombstone of an unfortunate explorer who disappeared in the Paris Catacombs.

A museum which takes visitors to the côté obscure of Paris.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.

In this Parisian garden's grotesque former life as a zoo it fed exotic animals to the bourgeois and put humans on exhibit.

A 16th-century fountain marks the site of a lost medieval cemetery once filled with mass graves.

The recovered bones of martyrs slaughtered during The Terror are on display in this church crypt.