There’s a special club house at the top for the bell ringers.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

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

The Byzantine, pre-Columbian, and medieval art at this stately mansion are some of the most under-appreciated collections in D.C.

A historic estate packed with George Washington's heirlooms, and its own nuclear bunker.

People escaping slavery may have hidden inside a corpse vault.

This shifting North Carolina sand dune is an odd little desert surrounded by oceanic forest life.

The remains of one of America's first radiation testing grounds still rest ominously in a Georgia forest.

Once the largest trading firm of enslaved people in the U.S., this building is now a museum that preserves Alexandria's dark past.

At 207 feet, one of the world's longest continuous escalators.

A museum cafe showcases Native American dishes and indigenous ingredients from across the Western Hemisphere.

A secret greenspace hides atop a Capitol parking garage.

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The tunnel under the Capitol Building where Congress takes out its trash.

After his presidency, George Washington planned to live only a few blocks from the Capitol building.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

The 28,000-year-old specimen is remarkably intact.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

Perhaps the most scandalous statue of America's first president.

This taxidermy horse was a Civil War hero.

The most decorated dog of World War I is preserved in the Smithsonian.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.