Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.

An original apothecary from 1792.

Edgar Allan Poe's old dorm is now a shrine to the author's legacy.

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

Paranormal investigators claim this abandoned asylum is the most haunted spot in the eastern U.S.

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.

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

A brass and marble scale model of the solar system embedded in the concrete.

Garments from across the globe call this hidden gem home.

This groundbreaking 16th-century map is known as "America's birth certificate."

An ear-piercing buzzer calls lawmakers to a vote with a series of long and short rings to form coded messages.

Corn-inthian columns with a uniquely American take on neoclassical architecture.

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

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.

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

Senators used to relax in the nearly forgotten marble tubs now hidden in the U.S. Capitol Building's basement.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

The institution is sitting on a goldmine of 21,000 paints, varnishes, pigments, and primers preserved for posterity.

An easily overlooked memorial to a Ukrainian famine-genocide that killed over 4 million people.

A hoard of sky catalogs, astrophysical journals, even the works of Galileo and Copernicus.

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

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