Warsaw's fantastically preserved gasworks...almost.

Romans built the world's tallest artificial waterfall in 271 BC.

A 16th-century horror show built in a lovely Italian garden.

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

Caligula's colossal pleasure ships, discovered by Mussolini only to be lost in flames.

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

Jesus' footprints and the first catacombs in the world.

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

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

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 final resting place of the poets Shelley and Keats.

A fairy tale castle in modern Rome.

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

Architectureal fantasy quarter of Rome.

The former home of an Italian artist is now a shrine to his ambitious works.

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

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

The Pope’s secret escape route.

The mystic whose incorrupt corpse still attracts the faithful.

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

Charles Dickens was not a fan of the ghastly wall dressings in this 6th century church.

A collection of objects supposedly singed by the hands of souls in purgatory.

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

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