One of the best places to see feral Colonial Spanish Mustangs in the United States.

Scattered around Atlanta are little doors with big charm.

An underground magnet for ever-changing street art.

Tour the sci-fi-esque reality of governmental disease management.

The fountains of the U.S. Navy Memorial are annually salted with water from the Seven Seas as part of a nautical ritual.

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

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

A historic arena where the Beatles played their first concert in the U.S.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

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

This lovely pocket park is one of the most under appreciated in D.C.

The oldest continuously operating fish market in the United States.

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

Rumor has it the uncarved lump behind the three famous suffragists is reserved for the first woman president.

Four bald cypress trees in Lafayette Square, across from the White House, mark the southern edge of a 100,000 year old cypress swamp.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

The winding route passes through an enclosed alleyway, two tunnels, and leads to the White House basement.

A nostalgic bibliographic gem.

The walls of the iconic dome are hollow and have a secret stairway.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

The country's oldest continually-operated mini golf course lies hidden in plain sight, eclipsed by one of D.C.'s most popular tourist attractions.

A painfully obvious spy house sits right across the street from the Russian Embassy.

A derelict bit of transportation infrastructure hidden in the woods.