Parking garage where Bob Woodward met Watergate source "Deep Throat."

This golfball sized platinum iridium cylinder is the official starting point for all national weight calibrations

The U.S. Air Force has an anti-satellite laser weapon.

Military and first responders can test their skills in a Foggy Bottom mock station down in Georgia.

This private island is still in the family after a 400-year history including a witch hunt and a pirate.

The Pentagon is so large that it was planned like a city, complete with internal highway infrastructure.

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

The Bong-area park police have asked visitors to please, stop stealing the signs.

There's a crumbling old mansion inside the Smithsonian National Zoo.

The oldest orange tree in California spawned a generation of citrus farmers.

Built by the patriotic residents of Boonsboro in a single day.

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

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

A rare wayfinding portmanteau of “Street” and “Avenue.”

Conveniently located within binocular range of a nuclear bunker, the "summer camp" area was a painfully obvious spy house.

A century-old network of freight tunnels underneath the city's historic business district.

The U.S. government built the million-pound stack of steel during the Space Race.

Portland had a unique approach to Cold War-era protections.

This unique historical monument features large concrete spheres designed to resemble fallen stars.

This doorless 20th-century elevator doesn't stop or slow down.

Chevron maintains one “Standard” brand station per state so it doesn’t lose the trademark.

This Manhattan skyscraper is a reminder of the brief but glorious age of urban air taxis.

The White House Situation Room was taken apart in 2006 and shipped to the Ronald Reagan Presidential Library.