These caves secretly held national treasures during World War II.

The oldest standing Byzantine church in Athens is tucked within a monastery in the middle of an upscale shopping district.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

A quirky bookstore hidden beneath a sea of whitewashed Greek villas.

A former factory serves as a shrine to the industry that sustained Santorini for decades.

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

A Bronze age settlement on the Greek island of Santorini might have been the inspiration for Plato's Atlantis.

Inside this building is another country within Rome, a sovereign entity without a physical territory.

One of Rome's most picturesque and original bridges was also a popular choice for Grand Tour artists.

Hidden within this iconic mountain are a set of World War II bunkers once used by German forces.

Also known as the Square Colosseum, this building is a prime example of fascist-era rationalist architecture.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

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

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

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

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

2300-year-old Roman road connecting the empire.

One of America's first planned communities is preserved in a state park.

This mosaic-covered bar is brimming with curated curios.

Once an ornate movie theater remade by Catholic Charities.

A 400-foot-tall tall map of Chicago makes this once-ignored building stand out.

You can take a class, browse the library, or visit the lavish lair of an international men's humor society.

In a quiet north Chicago neighborhood rests a stunning relic of the golden age of earthenware design.

Home to a protest movement, a bombing, and a dramatic change in labor history.