The Acropolis in Athens, the Elysee Palace in Paris and even the Giza Pyramids and Sphynx in Egypt all plunged into darkness as the power dimmed.
Berlin, Germany also took part in the World Wide Fund for Nature event. A city government official along with a WWF employee pushed a symbolic light switch, turning the hydro off to the Brandenburg Gate. The climate change event was first held in Sydney in 2007, and has since become a global phenomenon.
This year was the largest by far with millions of people shutting off their lights and appliance all over the world. Some 4,000 cities in more than 120 countries participated.
Did you participate in Earth Hour? If so, we want to see how! Click on the photos link above to send your pictures in.