This monument to a veteran of the Mexican-American War is one of only two in Manhattan that serve as an actual mausoleum.

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.

Built as a gift to the hottest tastemaker of the time, these hidden quarters remain an Art Deco showpiece.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

An overlooked memorial honoring the local Washington residents who died in World War I.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

The national park was once a plantation estate.

It was once the base for a series of domestic terror attacks.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

Home to items never before seen by the public.

An interesting decoration on this historic site, this weathervane comes with as many legends as it does questions.

American revolutionaries and British soldiers alike are buried here in the fourth-ever cemetery in Boston.

A former waterfront market is now in the center of town due to some interesting Boston engineering.

This monument on Breed's Hill proves that one of the most famous battles of the Revolutionary War is misnamed.

The tomb of Increase Mather and his son Cotton, influential colonial ministers obsessed with the occult.

Berthed at the Charlestown Navy Yard in Boston, "Old Ironsides" is the oldest commissioned warship still afloat.

The site of Paul Revere's historic two lantern warning.