While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

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

This sandwich shop has a century-old elevator behind a sheet of plexiglass.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

The "lovely red Vega" of the legendary record-settling pilot.

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

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

Largest Roman Catholic church in North America.

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

The walls of the iconic dome are hollow and have a secret stairway.

People escaping slavery may have hidden inside a corpse vault.

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

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

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 tragic reality of a town riddled with rumors of haunts, chemical spills, and serial killers.

This campus museum commemorates a national tragedy.

Inside houses a vast collection of military aircraft and missiles spanning the ages.

When a guy acquired a free church, he hauled it away piece-by-piece to make it the tasting hall at his vineyard.

Memorials and tributes scattered across the university grounds remember a famous national tragedy of the Nixon era.

The only depiction of Abraham Lincoln holding a weapon, and the names of all 9,000 Cuyahoga veterans of the Civil War.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

For decades, this waterfall remained hidden because of an artificial dam.

The 25th President's marble casket can be visited in this classical Ohio tomb.