Built hundreds of years ago this downtown iron barrier once protected a much despised king.

This historic address is home to the beloved ball and is an almost totally empty building among the most expensive real estate in the world.

This sculpture by artist Fritz Keonig survived the 9/11 attacks and now stands as a monument to the victims.

Elevated freight railway turned wildly successful urban park.

Final resting place of Typhoid Mary.

The first and only carousel with a lineup entirely of insects.

Giant acorn-shaped 19th century gazebo from which suburban Washingtonians gazed upon the original "silver" spring.

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

FDR's Art Deco hospital tower was hopelessly inefficient.

She stares out across six lanes of traffic, clutching a musket and infant with determination.

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

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

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

Bar full of oddities, specimens, artifacts and homages to the great dime museums of the past.

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

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

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

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

An overlooked oasis of quiet on the grounds of Washington's monumental basilica.

The oldest continuously operating fish market in the United States.

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

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

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

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