At almost 1,000 years old, this is the oldest known door in all of Britain.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This ancient Egyptian obelisk still bears the wounds of World War I.

Giant, friendly pelicans in Central London, the most unlikely of places.

Decades before the scandal, this staircase on the river was a literal "water gate."

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

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

Before Nixon, "watergate" meant canals.

The national park was once a plantation estate.

The controversial urban planner who designed Washington, D.C., was buried in Maryland, and can presently be found in Virginia.

Soldiers were buried next to Lee's house in the center of Arlington Cemetery to dissuade the general from reclaiming his property after the war.

Recorded as the first person buried in Arlington Cemetery.

The rogue roots are gradually consuming some of the historic marble grave markers.

A celebrity from the late Cretaceous period.

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

At 207 feet, one of the world's longest continuous escalators.

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

This historic boathouse was constructed using salvaged lumber from burned barns.

A suburban museum tells the story of a historic transportation network and even provides rides in antique trolley cars.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

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

The longest escalator in the Western Hemisphere takes over three minutes to ride down.

The tallest The Church of Jesus Christ of Latter-day Saints temple in the world soars above the Beltway.

Once home to seven different roller coasters, Glen Echo has undergone many transformations since its founding in 1891.