The sculpture is made of more than 100,000 knives collected to raise awareness about violence.

Far from the shore, this sandy victim of the Skeleton Coast looks like it was plopped in the middle of the desert.

The U.S. Fish Commission’s effort to mass produce carp.

Amid the sprawling Defense Intelligence Agency Headquarters is one of Washington's least accessible museums.

This restaurant has been a haven for D.C.'s LGBTQ community since the 1950s.

100 years later, they're still down there.

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

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

Where the U.S. government kept its actual treasure, before Fort Knox.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

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

An atomic bomb-proof strongbox protects the U.S. Constitution from terrorists and thieves.

Cold War intelligence agents monitored communist embassies from an attic in a former pigeon coop.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

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

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

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

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

Come for the waffles, stay for more waffles.

Constructed in the 1920s, this former pencil factory is now an office building.

This anonymous businessman sculpted in bronze became an enduring memorial after 9/11, and had been mistaken by rescue workers for a survivor in the rubble.

The longest continuous underwater road in North America was built at the insistence of Franklin Roosevelt.

Once thought to be the fabled Holy Grail, it is now known to be an oil lamp.

A memorial marks the library lobby where Langston Hughes' ashes are buried.