A celebrity from the late Cretaceous period.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The unique traffic pattern named for an influential urban planner is also known as the Pedestrian Scramble.

Washington's iconic carousel has a nice piece of Civil Rights history.

This mysterious structure by the Washington Monument is a flood barrier designed to protect the White House against rising waters.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

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

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

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

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The most accurate timepiece in the world.

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

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

The only National Monument ever to go missing for nearly 50 years then resurface in a dump.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

Go take a picture with the inventor of the daguerreotype photographic process.

Before Nixon, "watergate" meant canals.

A portal into the bricked up canal that runs through the heart of Washington D.C.

A 18th century graveyard and its astonishing cortege of macabre iconography.

A church that bred legends, and served as an inspiration for the Da Vinci Code.

Macabre astrological automaton clock dating to the late 1400s.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

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