This sprawling mini-golf empire is an impressive testament to a disappearing attraction.

This castle was established by the 4th Duke of Montrose and is connected to the Buchanan Clan.

A bizarre roadside attraction and the first instance of miniature golf in the world.

These abandoned waterworks are crumbling into the Potomac River.

A fantastic array of trays and cables once whisked books over to the Capitol at 600 feet per minute.

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

There's a crumbling old mansion inside the Smithsonian National Zoo.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

During the Industrial Revolution this “Temple of Invention” was full of intricate miniature machines and gadgets.

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.

Franciscan monks created a facsimile of the Holy Land for North Americans who couldn’t afford the trip overseas.

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

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

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

Home to items never before seen by the public.

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

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

This stately building in Alexandria, Virginia was built by Freemasons to honor one of their most famous members.

The semi-reclaimed ruins of this canal were once part of an ambitious plan to reroute the mighty potomac.

Enjoy a slice while browsing the world's largest collection of pizza memorabilia.

Current docking place of the SS United States, the fastest transatlantic ocean liner.

These disused steel furnaces are now haunting ruins that may one day be a national park.