The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

Daredevil repair workers can worm their way out the access hatch, loop ropes over the apex and rappel down the monument.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

A tiny monument to the unsuccessful attempt by Thomas Jefferson to place the prime meridian in Washington.

There just so happens to be a court even higher than the U.S Supreme Court: a basketball court in the building itself.

100 years later, they're still down there.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

A building shaped like the Army Corps of Engineers logo, because why not?

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

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

The monument's pointy aluminum tip has been melted down by repeated lightning strikes.

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

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

The span is crooked and made from two older recycled bridges.

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

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

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

The most accurate timepiece in the world.

The hidden offices underneath Memorial Bridge have been locked up since 1976.

Home to a vast and influential collection of Shakespeareana.

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

These abandoned grain silos and tunnels are an urban exploration dream.

This $3 million model train takes you through Chicago, Seattle, and the thousands of miles in between.