A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

A 17th-century doorway in a small Sabine village is a portal into the mysteries of alchemy.

A medieval house with mysterious alchemical inscriptions on its facade

A museum of alchemy and a basement laboratory all housed in an ancient building in a Gothic tower.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

Legend says this mysterious stone head belongs to a woman who was petrified by an alchemist.

Remnants of a 4th-century church with vivid medieval frescoes and ancient sarcophagi hide beneath this old basilica.

A wunderkammer of curious objects and intriguing art nestled within a hub of ancient Roman sites.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

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

The underground sanctuary of a mysterious ancient cult.

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

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

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

The comedy and tragedy of Oscar Wilde is preserved in a Dublin park, captured in a sculpture of colorful stone.

The oldest public library in Ireland.

This permanent collection of preserved bodies taken from Irish bogs is one of the leading authorities on such morbid mummies.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

The hidden lair of an alchemist rediscovered in a 2002 flood.