This bug-eyed water wheel uses the power of the Sun to clean up Baltimore Harbor.

Exact replica of the ancient monument, but much, much lighter.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

The Aldie Gristmill was once the largest factory of its kind in Loudoun County.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

This nine-story building is the oldest standing skyscraper in D.C.

D.C. once had its own tiny rival to the New York Stock Exchange.

A historic ruin just 20 feet away from a busy highway onramp.

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

A bit of retro transportation flair preserved in the world's largest department store.

A historic 1890s architectural masterpiece with an iconic clock tower that, once open to the public, now faces an uncertain future.

This wall on a street corner in Lower Manhattan has been a blank canvas for a rotation of renowned artists since the 1980s.

Historical figures from New York City's Catholic community reside in Midtown.

A hip bar decorated with walls of golden skulls.

Imagine having a street run right through your home, or better yet, a historic bridge three stories high.

The last remnants of what was once one of the world's grandest hotels can now be found in a Manhattan subway station.

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

The sounds of the world's largest fully functioning pipe organ dazzle shoppers at a Philadelphia Macy's.

The first American department store, and home to the largest operating musical instrument in the world.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.