One of the three perfect vellum copies of this historic book known to exist is on display in a specially-designed case.

This groundbreaking 16th-century map is known as "America's birth certificate."

A rotating cast of guys and dolls in front of a Washington, D.C. building.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

A spectacular tribute to statesman and philanthropist Andrew Mellon.

The story behind this beloved toy—named for Theodore Roosevelt and owned by his grandson—is more complicated than you might guess.

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

A tribute to the pop culture icon overlooks this Washington D.C. intersection.

There’s a special club house at the top for the bell ringers.

Where you can hail your favorite fictional commanders-in-chief.

The most accurate timepiece in the world.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

This forlorn park is the result of a failed investment turned tax dodge.

A human attendant once directed car traffic from this structure before automated stoplights.

One of America's first spies started out as a teacher in this little red one-room schoolhouse.

A failed piece of Orientalism has become the proud symbol of a community.

A priceless collection of the Nation's cryptologic history.

One of the U.S. Forest Service's only mansions is outfitted with a dinner table for floating food.

Mysterious rocks that ring musically when struck.

This beloved marketplace mascot poops money and grants good luck.

South Philadelphia is home to Keith Haring's only surviving in situ collaborative public mural.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

This large garden vase urn has nothing to do with the seventh U.S. President—it was designed by one landscape designer to honor another landscape designer's contributions to the National Mall.