This skeletal, unfinished Gothic church once housed a miraculous masterpiece by Raphael.

Haunting graffiti left by prisoners of the Spanish Inquisition.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

Every inch of this chapel is covered in craftsmanship from across the world.

This triumphal 16th-century arched gateway leads to the oldest street in Palermo.

Why a column on the entrance is inscribed with a verse from the Quran is one of Sicily's many mysteries.

A band of aerialists and circus performers putting on incredible shows in East Williamsburg.

A B.Y.O.B. Mexican cantina lives inside one of the last tortilla factories in Brooklyn.

Head past the aisles of tropical fruit and imported candy at this bodega to discover a hidden, weekends-only taco stand.

An everyday Jackson Heights bodega conceals a Mexican seafood paradise.

A young woman's senseless murder led to the controversial psychological theory of the "bystander effect."

This futuristic airport terminal was abandoned for decades before reopening as a hotel—with a vintage plane of its own parked out back.

A long abandoned hospital building on the outskirts of NYC.

The oldest private residence in New York City.

The oldest pastificio in Queens offers visitors fresh noodles and a peek inside the macaroni-making magic.

Some of New York's best tacos can be found in the back of an unassuming bodega in Queens.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

The secret medieval communication system will whisk your words above the noise of the crowd.

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

One of the oldest medical collections in Europe focusing on rare surgical instruments.

Peek through the gates at this oasis from the city, full of Old English charm.

The name of this tiny pocket park tucked between two buildings on Manhattan's Upper West Side is Latin for its location: "seventy-one."

This Manhattan museum houses one of the largest collections of Spanish art and manuscripts outside of Spain.