Gladiators once walked this ancient, subterranean passage.

A stunning little chapel built on a rock in the Mediterranean Sea on the Greek island of Leros.

Two churches shoot bottle rockets at each others' bell towers in an unusual Easter celebration.

This black sand beach was crafted from volcanic explosions including the historic Minoan eruption.

An intricate network of underground tombs carved into volcanic rock.

This medieval "painted village" is famous for its geometric facades.

This smily stone feline is meant to represent a mythical lion that almost destroyed the island of Kea.

Perched on a spindly rock spire in a Greek archipelago, this lighthouse would make a perfect wizard's tower.

Replicas of Apollo's leonine stone guard cats still line a sacred row in Greece.

Have tea in a cemetery with a dazzling view of Istanbul.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.

An Art Nouveau gem hides beneath the layers of city grime obscuring this once-magnificent building.

A gorgeous, Gaudí-esque stairway constructed in the city of Istanbul by a prominent Jewish family.

The ornate miniature mansions were built for Istanbul's feathered residents.

A marvel of Byzantine engineering under the streets of Istanbul.

A magnificent waterfall is also home to the remains of a Roman hydraulic engineering system.

The Pope’s secret escape route.

A forgotten "city of water" underneath the famous Trevi district.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

Rat sculptures try to infiltrate the Graybar Building in an architectural tribute to New York City's nautical history.

Cheap pizza and all of your naughty bedroom needs housed in a stunning example of Art Nouveau architecture.

Long-forgotten artifacts give incredible insight into New York's most glamorous hotel.

Seriously good slices of Sicilian pizza lurk at the back of the Bronx's oldest enclosed market.