A hundred-year-old museum filled with giant physics toys and experiments designed by grad students.

Where experiments are conducted on all things wood.

"Looks so real, it's scary!"

Now a living classroom, this house was once the home of Reverend James Clinton Dent, a formerly enslaved man and a pastor.

Depending on who you ask, this controversial treehouse is either a charmingly creative child's playhouse or an illegal encroachment on public land.

The innocent intentions of this monument are somewhat lost in the sculpture's muscled imagery.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

For 60 years, the academy had no permanent location until members voted Washington D.C. as its forever home.

The towering figures were created from the cemetery's fallen old-growth trees.

The most accurate timepiece in the world.

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

A lovely aquatic park built by a one-armed Civil War veteran who made a fortune from lotuses.

The United States Capitol's former columns still stand.