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

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

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

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

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

An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

When it opened during the final years of the embargo, all the drinks and cigars were free.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

This stunning blue and gold room changed cities twice before becoming part of the Smithsonian.

An Industrial Revolution-era public work that purified water using nothing but sand.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

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

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

America's first nuclear-powered merchant ship is now a time warp to the atomic age.

Where infamous mobster and leader of Murder Inc. Albert Anastasia made his home.

A young woman's senseless murder led to the controversial psychological theory of the "bystander effect."

A hidden bar inside an ad agency has a deliberately misleading name, so employees can stay late under pretext of paperwork.

A plaque immortalizes the spot where the early American spy said his famous last words: "I only regret that I have but one life to lose for my country."

Obscure and obsolete publications are given new life as works of art.

Offbeat arts organization that hosts exhibitions, events, and explorations.

A Manhattan office building is home to the world's largest chess board.

The notorious headquarters of a corrupt political machine.

New York City's only radical feminist independent bookstore.