An overlooked memorial honoring the local Washington residents who died in World War I.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

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

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

"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!”

Home to items never before seen by the public.

The oldest continuously operating fish market in the United States.

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.

The United States Capitol's former columns still stand.

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

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

Largest Roman Catholic church in North America.

A tribute to the pop culture icon overlooks this Washington D.C. intersection.

When it comes to handsignals (and colonialism) rock always beats scissors.

The most accurate timepiece in the world.

There’s a special club house at the top for the bell ringers.

A tiny piece of the Moon is embedded in this stained glass masterpiece.