This museum offers an actual time machine back through Colorado's past.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

These abandoned waterworks are crumbling into the Potomac River.

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

A building shaped like the Army Corps of Engineers logo, because why not?

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

A painfully obvious spy house sits right across the street from the Russian Embassy.

When it comes to handsignals (and colonialism) rock always beats scissors.

These recently uncovered walls are all that's left of Washington, D.C's first defense contractor.

A derelict bit of transportation infrastructure hidden in the woods.

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

The site of the climactic scene from the classic horror film is now a historic landmark.

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.

Before Nixon, "watergate" meant canals.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

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

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

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

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

Decades before the scandal, this staircase on the river was a literal "water gate."

The national park was once a plantation estate.

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