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

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

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

The U.S. Fish Commission’s effort to mass produce carp.

This statue of one of baseball’s greatest pitchers looks like something out of a sci-fi horror movie.

Every drop of D.C. tap water flows through this old waterworks.

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

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

The resting place of a Civil War celebrity's amputated limb.

These massive concrete balls were used to mine gold in Virginia.

Government testing at the asylum briefly explored using marijuana as a "truth serum" on Nazi prisoners of war.

These abandoned waterworks are crumbling into the Potomac River.

Helen Keller once broke ground on this historic center for the study of technologies to benefit the hearing impaired.

‘Bush the old fire dog died of poison July 5th, 1869. RIP.’

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

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

The system of air guns are fired off remotely to scare any trespassing avians.

A memorial dedicated to a highly decorated Marine and Korean War veteran, who also happened to be a horse.

This former Cold War missile control site played an important role in the creation of GPS.

An out-of-place Air Force radar dome is all that denotes this park as a former missile launch site.

Where pardoned turkeys once spent their all-too-brief final days.

Volcanic stone sentinels stand watch at a Korean Bell Garden in Virginia.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

D.C. once had its own tiny rival to the New York Stock Exchange.