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

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

This forgotten boat elevator was an engineering marvel in its heyday.

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.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

Before Nixon, "watergate" meant canals.

The towering figures were created from the cemetery's fallen old-growth trees.

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

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

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

A celebrity from the late Cretaceous period.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

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

The first presidential bomb shelter was located in an old vault under the Treasury, connected to the White House via tunnel.

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

This poor little statue is the most vandalized memorial in Washington.

When it opened during the final years of the embargo, all the drinks and cigars were free.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

It was once the base for a series of domestic terror attacks.

A small triangle of DC grass is the final resting place of one of Sonny and Cher's songs.