After Sierra Leone's railways shut down in 1974, a collection of engines and other artifacts spent decades hidden away in this old workshop—now a museum.

Sample sweets at an Art Nouveau candy shop that's been in business since 1874.

The last remains of one of the oldest and largest oak trees in the United States calls this state park home.

The oldest of its kind in the country, this tree sits where formerly enslaved people are said to have founded the city of Freetown.

This unacceptably tall building was the real reason for Washington, D.C.'s skyscraper ban.

Long buried under the 20th-century landscape, this lift lock of the Alexandria Canal is the lone remnant of an ambitious early American transportation project.

The final resting place of an unidentified revolutionary soldier sits behind a Virginia church.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

The narrowest house in America is seven feet of pure spite.

This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

The "Key of Keys" for Washington, D.C. and the apocryphal landing place for the military campaign that started George Washington's career is now at the bottom of a well.

A hill outside of Kasempa is the location of a famous battle between the Kaonde and Lozi tribes.

The oldest continuously operating fish market in the United States.

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

The 28,000-year-old specimen is remarkably intact.

A surprising, but overlooked example of geology in the middle of the nation’s capital.

This bridge over D.C.'s Rock Creek Park is sometimes called the "Buffalo Bridge" because of its four buffalo sculptures, which were cast from a single piece of bronze.

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

This statue of the "father of television" stands prominently in the United States Capitol.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

A line of blue paint marks the route of the inaugural parade.

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.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.