Water and windows define this defensive Italian well.

One of seven Jewish catacombs in Rome and one of only two open to the public.

A modern sliver of architecture in Roma.

The Pope’s secret escape route.

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

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

This picturesque Umbrian city has a subterranean side that has long remained hidden.

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

Gigantic mosaic sculptures of the figures on Tarot cards fill this colorful Tuscan garden.

A hospital where antique dolls are given new life.

The famous sculptor left his mark on this Italian wall in an internationally protected example of street art.

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

This quaint Italian town keeps losing ground as the sides of its plateau slowly erode.

Jesus' footprints and the first catacombs in the world.

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

A fairy tale castle in modern Rome.

Venice's island of the dead.

A sunken idol welcomes parishioners to Davy Jones' Locker.

Go inside to really appreciate this 500-year-old technological masterpiece.

Medieval town turned hippie commune, once home to the secret foreskin of Jesus Christ.

The final resting place of the poets Shelley and Keats.

Pilgrimage site for star-crossed lovers.

Virgil's many-mouthed gateway to the underworld.