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

This domed temple was built in a hidden cave mouth as a refuge for sinners seeking absolution.

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

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

Natural cathedral designed by Italian artist Giuliano Mauri.

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

Submerged busts of communist and socialist figures from the USSR.

This ancient burial mound is accessed by an impressive Greek-built archway.

The saltiest lake in all of Crimea is also the pinkest of the pink and teeming with life.

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

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

Geothermal waterfalls in Tuscany.

Renaissance villa and gardens complete with a tormented colossus.

Stalactites and stalagmites in a beautifully lit cave.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

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

100 year tradition of fist fights, marked by marble footsteps.

Venice's "Island of the Mad."

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

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

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

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

Virgil's many-mouthed gateway to the underworld.

Pompeii's less famous neighbor is still revealing her secrets.