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

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

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

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

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Once the supplier for noteworthy projects like the National Cathedral, this old brickworks now lies abandoned.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

Inmates dig the graves at the largest prison cemetery in the U.S., the final resting place of both cowboys and Indians.

An extensive, if one-sided, history of U.S. law enforcement's war on drugs.

Of course the grave of JFK's assassin is surrounded by conspiracy theories.

Where the U.S. government kept its actual treasure, before Fort Knox.

A wondrous old library overlooking the nation's capital.

The world's largest squirrel statue clutches a pecan bigger than your head.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

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

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

This is one really big nut.

A Prada store in the West Texas desert that is never open for business.

Remembering the Alamo with a full-scale replica of the 1836 city.

Mysterious glowing orbs float through the desert night.

A World War II officers' club features Old West murals painted by German POWs.

A mysterious "wedding cake" castle in the middle of the urban desert.