People partake in New York City's sixth annual, and the world's fourth annual Pillow Fight Day. (Jessica Rinaldi/Reuters)

Pillow fight! April 2 saw people in more than 100 cities around the world gather to celebrate the fine skill of wielding a pillow. “International Pillow Fight Day” started as part of the “Urban Playground” movement, meant to get people off their couches and into the city interacting with strangers. And interact they do, with feathers and abandon flying. See the full gallery of Washington’s pillow fight here.

Dr. Sun Yat-sen Memorial Hall in Taipei (Pichi Chuang)