This abandoned seaside fortress is now simply an imposing ruin being taken back by nature.

A building shaped like the Army Corps of Engineers logo, because why not?

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

The "lovely red Vega" of the legendary record-settling pilot.

Largest Roman Catholic church in North America.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A precariously balanced rock perches on the edge of a cliff created tens of thousands of years ago by glacial erosion.

Historic town settled in the 19th century because of its convenient location along a popular coal transport route.

A 10-foot-tall concrete Alley Oop statue left over from World War II now stands on the side of the road.

The oldest continuously inhabited street in America.

Oldest existing wire suspension bridge in the United States.

In upstate New York, gorgeous waterfalls and a watermill are slowly being reclaimed by nature.

This Art Deco fortress in upstate New York gives Manhattan's vaunted examples of the style a run for their money.

The shared home of a utopian commune that practiced "free love" a century before the hippies.

A historic recreation of the golden age of the Erie Canal, abandoned for some time, slowly being restored.

Once thought to be the fabled Holy Grail, it is now known to be an oil lamp.

Surrounded by low rise buildings and partially converted into an auto body shop, this marble archway is the only vestige of a forgotten Manhattan estate.

There's a piece of New York City transportation history hidden in plain sight at a Manhattan subway stop.

The most confusing clock in New York.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

An uber-secure, windowless tower of doom in the center of Manhattan is an NSA spyscraper.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

Curious crustaceans support an obelisk from ancient Egypt that now stands in modern-day Central Park.