A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

Venice's "Island of the Mad."

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

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

The martyr's wax-enhanced skeletal remains lie preserved in a glass case in the Santa Maria della Vittoria in Rome.

The Pope’s secret escape route.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

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

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

Limestone grottoes turns everyday objects into stone.

The quiet field that inspired one of the most famous songs of all time.

A visionary Italian architect created an impressive cluster of concrete structures for a family's private tomb.

A whale rib was used to advertise the store by the arch that offered exotic goods from far away.

A map of Italy made entirely of trees.

A cherry tree growing atop a mulberry tree.

Over 100 towers were built in Bologna during the Middle Ages, but only 22 survive.

A medieval fountain lined with 99 unique stone faces whose origins and meaning remain unknown.

Naturally preserved bodies are eerily staged throughout the crypt in varying poses.

Overlooked amid the tourist bustle of Florence, this museum is dedicated to the craft of stone inlay.

A modern sliver of architecture in Roma.

Crushed coral and crystals give the sand its signature coloration.

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

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

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