These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

Housing the National Women's Party since 1929, this historic house is now a monument to the fight for gender equality.

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

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.

The walls of the iconic dome are hollow and have a secret stairway.

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

A wondrous old library overlooking the nation's capital.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

Home to items never before seen by the public.

The United States Capitol's former columns still stand.

This surprising gem is a world-class archeological museum hidden at the University of Chicago.

A one-armed veteran of the Battle of Waterloo lies in a cemetery for one in the middle of a Chicago scrapyard.

Assemble a masterpiece at the first and only North American school exclusively dedicated to mosaic art.

One-of-a-kind preserved ruins of an abandoned 1880s church in Chicago's Pilsen neighborhood.

This morbid, delightful curiosity shop offers everything from animal bones to human teeth.

A European-style bath house in Chicago.

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

An antiquated German apothecary on Chicago's North Side.

A science teacher's dream.

Non-profit time travel mart sells goods you would need for a trip through the fourth dimension.