A clone-tree in Washington Square Park sprung from seeds that went to the Moon and back.

The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

Overlooking the Colorado Convention Center is this giant sculpture made from thousands of triangles.

A Rocky Mountain city provides a happy ending for a pinto pony and his Brobdingnagian red chair.

In the middle of a busy airport, a statue honoring the astronaut who told Houston that Apollo 13 had a problem.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

This landmark building is now a vibrant performing arts space with musical acts from around the world.

Dedicated to the art and science of glass in equal measure, this space is as much laboratory as museum.

This exhibit allows visitors to wander through the interior of a replica Ice Age glacial cave.

Pluto is still considered a planet in Ithaca, New York.

It would take 35 firetrucks to fill this enormous glacial pothole.

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

A dark patch of the ceiling at Grand Central Terminal which was not restored is still stained brown by tobacco.

Spinning silently in the lobby of an Art Deco masterwork is a massive vintage model of the Earth.

100 massive sculptures in the Hudson River Valley.

These unassuming lighthouses have seen the first reading of the Pledge of Allegiance, the first wireless transmission, and more than one mystery.

Rusting away on the edge of New Jersey are the remains of a Cold War missile launch site.

An abandoned subway tunnel that could have reinvigorated Staten Island still lies somewhere beneath this Brooklyn park.

A former poultry store that looks like a giant duck and is one of the "seven wonders" of Long Island.

This preserved wilderness hides the remains of a colonial grain mill used to feed George Washington's troops.

This museum-within-a-museum pays tribute to "The World's Most Experienced Airline."

An abandoned Gold Coast-era mansion once intended for the exiled ruler of Albania, who never arrived.

The remnants of two World's Fairs are here, complete with a 12-story globe, a mini-Manhattan, and a UFO-shaped pavilion.

No monkeying around, this fountain was really named after the classic sci-fi film.