An Industrial Revolution-era public work that purified water using nothing but sand.

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

This robust fence in front of a historic Georgetown home is likely made from hundreds of recycled Revolutionary War firearms.

The towering figures were created from the cemetery's fallen old-growth trees.

People escaping slavery may have hidden inside a corpse vault.

This grisly headstone doesn’t seem to be resting in peace.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

A diminutive memorial marks the site of a successful assassination by a right-wing death squad in America's capital.

A historic ruin just 20 feet away from a busy highway onramp.

Before Nixon, "watergate" meant canals.

Also known as the Founding Church of Scientology.

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

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

Behind an abandoned storefront is an example of pioneering 1930s gas station architecture.

An overlooked tribute to one of the most important peace deals in American history.

The first memorial dedicated solely to the Black troops who fought for the Union.

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

Daily lunch spot for many of Washington, D.C.'s cab drivers.

A rotating cast of guys and dolls in front of a Washington, D.C. building.

A bas relief commemorates the "Nuns of the Battlefield" who cared for soldiers on both sides of the conflict.

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

More than 500 unique and specially designed cases collected by D.C.'s "Harmonica Case Man."

The walls of the iconic dome are hollow and have a secret stairway.