Katy Perry attends the European premiere of Katy Perry: «Part Of Me 3D» at Empire Leicester Square on July 3, 2012 in London, England. (Photo by Mike Marsland)

Heavy artillery on parade during a review of the Moscow Garrison troops during the May Day celebrations in Red Square, passing posters of Lenin and Stalin. (Photo by N. Sitnikov/Hulton Archive/Getty Images). 1st May 1947

Pope John Paul II (1920–2005) is shot by would-be assassin Mehmet Ali Agca in St Peter's Square, 13th May 1981. His attendants help him into his white jeep after the incident. (Photo by Keystone/Hulton Archive/Getty Images)

(L-R) Daniel Radcliffe, Emma Watson, J K Rowling and Rupert Grint attend the World Premiere of “Harry Potter And The Deathly Hallows: Part 1” held at The Odeon Leicester Square on November 11, 2010 in London, England. (Photo by Dave Hogan/Getty Images)

Actress Emma Watson attends the World Premiere of Harry Potter and The Deathly Hallows – Part 2 at Trafalgar Square on July 7, 2011 in London, England. (Photo by Ian Gavan/Getty Images)

Rowan Atkinson attends the UK premiere of Johnny English Reborn at The Empire Leicester Square on October 2, 2011 in London, United Kingdom. (Photo by Dave Hogan/Getty Images)

Actress Anne Hathaway attends the “The Dark Knight Rises” World Premiere at AMC Lincoln Square Theater on July 16, 2012 in New York City. (Photo by Jim Spellman)

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.