This 29-ton granite ball spins around at the slightest touch thanks to a scientific phenomenon.

The skeletal white beams stand as a monument to religious dissent.

An original apothecary from 1792.

The highest point in Virginia can only be reached by passing through ponies and flowers.

Exact replica of the ancient monument, but much, much lighter.

Outsider art meets paleontology at this roadside reptile repository.

A secretive collection featuring objects that were designed specifically for U.S. intelligence operations.

A memorial to a shareholder activist feared by CEOs around the United States.

This grisly headstone doesn’t seem to be resting in peace.

An 18-mile-long tunnel for sewage waste will soon wind within the bowels of Washington, D.C.

Every drop of D.C. tap water flows through this old waterworks.

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

A portal into the bricked up canal that runs through the heart of Washington D.C.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

The school tested mustard gas for the U.S. Army during World War I.

The early data processor factory founded in Washington for the 1890 U.S. Census went on to become IBM.

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

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

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

A diminutive plaque recalls the treetop sniper who almost killed Abe Lincoln.

Before Nixon, "watergate" meant canals.

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

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