Last weekend, the National Building Museum in Washington, D.C., opened a 10,000 square-foot ball pit to the general public, and everyone cheered that, finally, someone made their childhood dreams come true.

A view of a vintage Rolls Royce limousine with a female driver. (Photo by General Photographic Agency/Getty Images). Circa 1935

A member of the German wireless police picks up signals on the radio equipment he carries on his back, while his colleague takes notes. (Photo by General Photographic Agency/Getty Images). Circa 1925

A workman takes a siesta on a girder during the building of Radio City, the city of New York spread out below. (Photo by General Photographic Agency/Getty Images). Circa 1933

Two guards perform an execution in China, one holding the gun, the other holding a mask over the victim's face. (Photo by General Photographic Agency/Getty Images). Circa 1925

A general view of the landslide-hit Miancu Village on July 3, 2011 in Maixian County, Sichuan Province of China. Eight people are still missing after a dormitory building of a chemical plant was hit by a rain-triggered mudslide in Maoxian County on Sunday morning. Rescue efforts are underway. (Photo by ChinaFotoPress/Getty Images)

Three Chinese soldiers at the time of a civil war in China. (Photo by General Photographic Agency/Getty Images). 1922

A general view of the Coe Collection of American Indian Art press view at the Metropolitan Museum of Art on December 19, 2011 in New York City. (Photo by Dario Cantatore/Getty Images)