Love is in the air along the small street in Brooklyn.

The site of a fallen tree that protected Americans from British forces during the American Revolution.

This elaborate tunnel is the first structure composed of cast concrete in the United States.

One of the remaining markers of an era when Brooklyn and Flatbush were separate cities.

This striking arch, one of the first architectural elements constructed in Prospect Park, was recently restored to its original glory.

Tucked in a nondescript downtown Brooklyn mall is a bar containing a remarkable turn of the century anatomical wax collection last seen in 1920s Berlin.

Sniff the Titan Arum's rotting flesh.

The one-stop shop for all of your superhero (or evil arch-nemesis) needs.

Ride the subways of yesteryear.

These caves secretly held national treasures during World War II.

Where commuters walk through remnants of an ancient Greek necropolis.

Large collection from the 3rd millennium BCE.

Legend says this sacred tree was a gift from goddess Athena.

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

An ancient octagonal weather station named for the eight Greek gods of wind.

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.

A 2,000-year-old computer demonstrates remarkable engineering and astronomical precision.

One of the most photographed locations in the entire city.

The middle finger of modernity.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

A long-buried ancient ruin unearthed right in the middle of the city.

One man's quest to fix his toilet unearthed over 5,000 artifacts spanning more than 2,000 years of history.