The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

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

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

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.

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

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

The most accurate timepiece in the world.

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

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

A celebrity from the late Cretaceous period.

Obscure Freemasons still live in D.C.’s largest private residence.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

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

A super-sized promotional trick that is now a D.C. landmark.

A haunting tribute to pioneering photographer Clover Adams.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

Largest Roman Catholic church in North America.

The oldest continuously operating fish market in the United States.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

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

The national park was once a plantation estate.

There’s a hidden military meme engraved on the World War II Memorial.