A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

This English-inspired Maryland garden is home to acres of opulent plant life including bushes shaped into an entire fox hunt.

A hidden alley in urban Baltimore is a haven for graffiti artists.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

The discovery site of the "Capitalsaurus," the official dinosaur of Washington, D.C.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

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

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 derelict bit of transportation infrastructure hidden in the woods.

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

A wondrous old library overlooking the nation's capital.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

This grand gothic brewery has been pumping out suds for over a hundred years.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.