This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

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

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

A huge enchanting public park just outside the ancient walls of Rome.

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

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

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

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

The Pope’s secret escape route.

Jesus' footprints and the first catacombs in the world.

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

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

The underground sanctuary of a mysterious ancient cult.

The yawning maw of this pagan visage is said to bite off the hands of liars.

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

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

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

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

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

The most visited, and possibly most controversial, museum in Germany.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

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

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

Medicinal spa created with the discharge from a geothermal energy plant.