For over 30 years the walls of this Harlem schoolyard have been a gallery of street art by "Kings and better."

A pedestrian island in the middle of world-famous Times Square emits a strange (and purposeful) humming noise.

The oldest surviving bridge in New York City, which reopened to pedestrians in 2015.

Mysterious 500-year-old tapestries depict a unicorn hunt.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Elevated freight railway turned wildly successful urban park.

A crumbling hospital from the 1850s on Roosevelt Island.

A terrific purveyor of natural history objects and curios.

These artifacts were discovered during the construction of the airport, with some dating back to the Neolithic period.

A preserved portion of an ancient Athens barrier is displayed in a hotel basement.

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

A staircase made of gravestones leads up to this church built into a giant rock.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

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

The ruined doorway is a portal to the building's turbulent and torturous past.

Where commuters walk through remnants of an ancient Greek necropolis.

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

This legendary city has been a tourist attraction for centuries.

The hallucinogenic center of the ancient world.

Monasteries on rock pillars, once accessible only by frayed ropes.

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

Giant marble phalluses on the sacred island of antiquity.