Mysterious tombstones thought to be remnants of Atlantis.

Stalactites and stalagmites in a beautifully lit cave.

Architectureal fantasy quarter of Rome.

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

Breathtaking and huge 430 year old maps of Italy.

The Pope’s secret escape route.

Architectural monsters are devouring this palace's every door and window.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

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

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

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

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

A Nesting Doll of Churches.

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

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

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

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

The underground sanctuary of a mysterious ancient cult.

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

Rome's semi-secret peephole vista is also a former Crusader stronghold.

The final resting place of the poets Shelley and Keats.

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

Jesus' footprints and the first catacombs in the world.