This whimsical Oz-themed park had a wonderful impact on the surrounding neighborhood.

All of Chicago's wood-paved streets are long gone but two alleys remain.

Rifle through images of skyscrapers, Worlds Fairs, and more in the largest public postcard repository in America.

A shining sculpture made of 3,115 lights, the number of visible stars in the Northern Hemisphere.

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

This memorial plaque remembers a strangely shallow maritime disaster known as "Chicago's Titanic."

The iconic Chicago sculpture hides a beautiful and easily overlooked plaque on the backside.

Hidden on the 7th floor of a historic building, this Cajun spot features wall-to-wall bottles of hot sauce.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

The only tennis court that falls under the jurisdiction of the central bank.

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

A small token of gratitude from freezing cold journalists who were given a warm haven while covering JFK's inauguration.

In the basement of the U.S. Capitol Building is a hidden storage room full of ornate floor tiles leftover from the 1850s.

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

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

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

The elevator that makes it possible to fly American flags in bulk over the U.S. Capitol

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

They sort through millions of dollars worth of diplomatic gifts on behalf of the government.

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

There's an old indoor swimming pool hidden directly underneath the White House Press Briefing Room.

The discovery site of the "Capitalsaurus," the official dinosaur of Washington, D.C.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.