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

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

An Italian hillside ghost town.

This 16th-century monastery has been turned into a surrealist architecture compound.

The final resting place of the poets Shelley and Keats.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

2300-year-old Roman road connecting the empire.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

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

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

The underground sanctuary of a mysterious ancient cult.

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

Stalactites and stalagmites in a beautifully lit cave.

The middle finger of modernity.

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

Architectureal fantasy quarter of Rome.

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

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

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

Originally a meeting place for foreign correspondents and war reporters, the FCC remains an atmospheric spot for sunset drinks in Phnom Penh.