The house where John Wilkes Booth conspired with his co-conspirators.

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

A haunting tribute to pioneering photographer Clover Adams.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

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

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

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

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

This grand gothic brewery has been pumping out suds for over a hundred years.

Home to items never before seen by the public.

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

The United States Capitol's former columns still stand.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

Where America's first doomsday cult awaited the end of the world.

Philadelphia boasts one of the best — and most often overlooked — traditional Japanese gardens in North America.

A rare view of a preserved Victorian science museum.

An abandoned cemetery lies in ruins as the surrounding forest swallows it whole.

A layered tribute to the work of mosaicist Isaiah Zagar.

Mural made of 100,000 pieces of hand blown glass, and until recently, the largest glass mural in the US.

Huge masonic hall in Philadelphia with lavishly themed rooms.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

The third tallest lighthouse in America once guided author Stephen Crane to safety.

The highest point in New Jersey is marked by a massive, if simply named, obelisk.

One of the U.S. Forest Service's only mansions is outfitted with a dinner table for floating food.