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

A celebrity from the late Cretaceous period.

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

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

The house where John Wilkes Booth conspired with his co-conspirators.

Largest Roman Catholic church in North America.

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

The oldest continuously operating fish market in the United States.

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

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

A derelict bit of transportation infrastructure hidden in the woods.

A painfully obvious spy house sits right across the street from the Russian Embassy.

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

Home to items never before seen by the public.

Also known as "Robin Hood's tree," this tree became a famed location along Hadrian's Wall before it was cut down in an act of vandalism.

A former major munitions plant that has been converted into a sprawling art space.

This brick-lined pedestrian walkway was once a railway tunnel used during the Civil War.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

The 72-foot giant escaped confinement in a large patch of mulch only to be reburied in the sandy shores of the Potomac River.

An abandoned stretch of highway, deteriorating next to the operational one.

An out-of-place Air Force radar dome is all that denotes this park as a former missile launch site.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

The highest point in Tennessee, Clingmans Dome bears witness to the ravages of one type of insect.

105-foot wide giant metallic flower blooms anew every day in the heart of Buenos Aires.