Last Saturday, March 23, iconic landmarks and skylines were plunged into darkness as people and businesses around the world participated in Earth Hour 2013, turning off their lights at 8:30 p.m. local time. Earth Hour was organized by the World Wildlife Fund in 2007 as a way to bring attention to energy consumption, sustainability, and climate change issues. More than 150 countries took part in last year's event, and the movement has spread even further, with Palestine, Tunisia, Suriname, and Rwanda among a host of newcomers pledging to take part this year. The images below (starting with photo number two) are interactive -- click on each image to "turn off the lights." (For wider screens, be sure to click the 1280px option below.)