Proto-CIA agents trained with grenades in the sand traps and fired machine guns from the fairways.

At Washington's Dulles Airport is a satellite museum (no pun intended) with three quarters of a million square feet of aircraft history.

These unusual rooms on wheels are holdovers from the 1960s.

An out-of-place Air Force radar dome is all that denotes this park as a former missile launch site.

A double agent hid information for the Soviet Union beneath this bridge for more than 20 years.

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.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

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

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

The most accurate timepiece in the world.

This imposing Masonic temple a mile from the White House was the first public library in Washington, D.C.

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

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

Home to items never before seen by the public.

This is the oldest Roman-made bridge in the city still existing in its original state.

Breathtaking and huge 430 year old maps of Italy.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The capital of the Cayman Islands is a center of offshore banking, but gets battered by blistering hurricanes.

A magical sinkhole on the Yucatán Peninsula is adorned with mini waterfalls and hanging vines.

A museum dedicated to the history and exploration of both popular music and science fiction.

The tech giant built three enormous glass orbs in Seattle so employees could work inside a rainforest greenhouse.

A massive sea stack famous for its appearance in The Goonies.