A former major munitions plant that has been converted into a sprawling art space.

This lovely picnic spot featuring thunderous jet landings is an aircraft spotter’s dream.

This pre-Revolutionary War grist mill ground corn and flour for soldiers in seven American wars.

At 207 feet, one of the world's longest continuous escalators.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

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

The oldest building in the District of Columbia was preserved because of a mistaken connection to George Washington.

Before Nixon, "watergate" meant canals.

Washington's iconic carousel has a nice piece of Civil Rights history.

The national park was once a plantation estate.

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

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

Largest Roman Catholic church in North America.

Fittingly, America's museum of architecture is itself a magnificently designed old building.

Home to items never before seen by the public.

A miniature city, once ruled by the Queen of the Netherlands.

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

Unsurprisingly, Holland is home to one of the most magnificent flower gardens in the world.

The sweet story of how American cargo planes became known as "Candy Bombers" during the Berlin Blockade.

This historic funicular system combines the old with the new while offering delightful views over the surrounding valley.

A preserved college lock-up that recalls a clubhouse approach to discipline.

Sitting in the basement of a castle, the largest wine barrel in the world is bigger than most apartments.

Originally envisioned by King Ludwig II to rival Versailles, Herrenchiemsee's "New Palace" remains half-gilded for lack of funds.