The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The tunnel under the Capitol Building where Congress takes out its trash.

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

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

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

"Congress may voluntarily remain in session throughout the summer, in order that our Congressmen may be protected from the intolerable discomforts and dangers of the ordinary outdoor weather!”

An overlooked memorial honoring the local Washington residents who died in World War I.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

There’s a hidden military meme engraved on the World War II Memorial.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

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

The largest arcade museum in the world chronicles the golden age of video games which ended promptly in 1987.

Birthplace of America's first documented serial killer.

The first "Hut" was actually a small brick building.

The grandson of a Kiowa chief created what has become the iconic symbol of a city on the Plains.

A mysterious and terrifying public art goblin seemingly meant to inspire local legend.

The lecture hall where Alexander Graham Bell first demonstrated the long-distance phone call.

Statue in Salem of the woman who starred as the witch Samantha in the sitcom "Bewitched."

The 340-year-old house that inspired the classic Nathaniel Hawthorne novel.

The only structure left with direct ties to the Salem witchcraft trials of 1692.

The 92-foot-tall structure is based on the aircraft that carried the first Americans into space.