A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

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.

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

A celebrity from the late Cretaceous period.

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

These unusual rooms on wheels are holdovers from the 1960s.

Railroad officials in the early 1900s sought to spare travelers the sight of Roman soldiers’ private parts.

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

A historic arena where the Beatles played their first concert in the U.S.

D.C. once had its own tiny rival to the New York Stock Exchange.

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

After James Madison's death, his wife and former First Lady Dolley Madison lived in this yellow building near the White House.

One of the last mosaic tile facades found in the city.

Home to items never before seen by the public.

The oldest continuously operating fish market in the United States.

Decades before the scandal, this staircase on the river was a literal "water gate."

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

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