The system of air guns are fired off remotely to scare any trespassing avians.

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

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

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

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

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

Washington's iconic carousel has a nice piece of Civil Rights history.

One of the dwarven trees dates back to 1625 and survived the Hiroshima bombing.

Art deco landmark on the outskirts of Washington, D.C.

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

An Industrial Revolution-era public work that purified water using nothing but sand.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

The United States Capitol's former columns still stand.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

Built by the patriotic residents of Boonsboro in a single day.

A modern ghost town whose inhabitants were driven away by the growth of nuclear power.

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

The rooster who crossed the road lives on forever in Takoma Park, Maryland.

An intricately designed junk art house with four extravagant junk art cars hidden in the suburbs.

An astounding collection of medical specimens, including bits of President Lincoln.

The world's oldest continuously operating airport was founded by the Wright Brothers.

The Forest Service's surprisingly sophisticated collection of wildfire prevention art features America's most beloved bear.