Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

This castle-like building in Manhattan helped destigmatize cancer in the 19th century.

Though strikingly beautiful, Seattle's other railway station is now largely forgotten.

This unassuming cheese empire in rural Oregon churns out more than 150,000 pounds of cheese each day.

One of the only single-person private gravesites in New York City.

Edison's cast-in-place concrete houses were a failure, but way ahead of their time.

Pulled from the rubble of one of the worst modern tragedies, a steel crossbeam became a symbol of hope for New Yorkers.

The capital of Cambodia is named after the hill on which this ancient temple complex stands.

This 40-room dwelling tucked within a cliff was built by the basin's prehistoric residents.

Large collection from the 3rd millennium BCE.

Its unique collection details the history of the state's svelte railroads.

Despite many attempts to finish this overpass, it has been abandoned since the 1970s.

Located just behind a quiet residential neighborhood, this is ground zero for the Salem witchcraft hysteria of 1692.

This ancient statue of Dionysus lies unfinished and abandoned in one of Greece's oldest quarries.

The fantastic charm of England's oldest botanical garden has made it a place of writerly inspiration for centuries.

St. Mary's features one of the most spectacularly decorated cathedral interiors in all of Europe.

Two large-scale sculptures of Adam and Eve greet visitors in the nude at the Time Warner Center in NYC.

Historic fortifications form the boundary of Vatican City, but it’s not entirely surrounded by walls.

A lush indoor jungle fills this bustling Madrid transportation hub.

When the Soviets destroyed the historic Armenian monastery they somehow left its bell tower intact.

Quito's historic, main square dates back to the 16th century.

This exceptionally well-preserved ancient marvel also houses a small museum dedicated to Jordanian folk tradition.

Revolutionary War casualties fill the only 17th century structure remaining in Manhattan.

The highest point on the island known for buildings that touch the sky.