Actresses Zelda Williams and Kelly Monaco attend Nintendo's celebration of the launch of Super Mario 3D Land at Siren Studios on November 3, 2011 in Hollywood, California. (Photo by Jason Merritt/Getty Images for Nintendo)

People play Taiji on a square on August 08, 2011 in Luoyang, Henan Province of China. People all over China mark National Fitness Day on Monday in their own ways. (Photo by ChinaFotoPress/Getty Images)

The crowd is reflected in the glasses of a bearded competitor at the third annual National Beard and Moustache Championships in Las Vegas, Nevada on November 11, 2012. (Photo by Frederic J. Brown/AFP Photo)

Miss Lithuania, Patricija Belousova, poses for the judges, during the national costume show during the 63rd annual Miss Universe Competition in Miami, Fla., Wednesday, January 21, 2015. (Photo by J. Pat Carter/AP Photo)

In this handout from the Ministry of Defence, Royal Air Force VC10 and Tristar air-to-air refuelling aircraft support the first UK air combat mission in support of UN Resolution 1973 in flight on March 19, 2011. Col Muammar Gaddafi has vowed a “long war” against the “crusader aggression” after over 100 missiles were fired by the US and UK, during multi-national action aimed at enforcing a UN-mandated no-fly zone. (Photo by SAC Neil Chapman/MoD via Getty Images)

The National September 11 Memorial & Museum (branded as 9/11 Memorial and 9/11 Memorial Museum) is the principal memorial and museum commemorating the September 11 attacks of 2001, which killed nearly 3,000 people, and the World Trade Center bombing of 1993, which killed six. The memorial is located at the World Trade Center site, on the former location of the Twin Towers, which were destroyed during the attacks. The World Trade Center Memorial Foundation was renamed the National September 11 Memorial & Museum at the World Trade Center in 2007.

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 girl holds up a photo of Pope Benedict XVI which reads “tear his face” during a protest against the World Youth Day 2011 celebrations taking place on August 17, 2011 in Madrid, Spain. Initiated by Pope John Paul II in 1985, World Youth Day youth-oriented events for the celebration of the Catholic faith are held every three years in a different country; this time in Madrid from August 16 – 21, with Pope Benedict XVI in attendance. (Photo by Denis Doyle/Getty Images)