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

An obscure federal monument honors the French diplomat who served as Ambassador to the U.S. during WWI.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Was there a small "backpack nuke" hidden in the attic? JFK apparently thought so.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

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

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

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The national park was once a plantation estate.

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

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

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.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

Largest Roman Catholic church in North America.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

The most decorated dog of World War I is preserved in the Smithsonian.

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

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.