The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Richard III supposedly disposed of his nephews' bodies here in an effort to seal his claim to the throne.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

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

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

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

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

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.

This landmark of the Chicago silent film industry may not be in the picture business anymore but it still stands proudly.

Hear the quietest sound from across the dome.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

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

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

A former major munitions plant that has been converted into a sprawling art space.

This rare triple-jurisdiction drawbridge passes through Virginia, Maryland, and Washington, D.C.

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

Before Nixon, "watergate" meant canals.

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

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

One critic described it as "middle Mussolini, early Ramses, and late Neiman-Marcus." Another called it an architectural "natural disaster."

The iconic D.C. restaurant where the Cuban Missile Crisis was negotiated, now a Walgreens.

The most accurate timepiece in the world.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.