A Christmas tree decorated with 8,000 lights that are charged by 15 stationary bicycles is seen in Puebla December 16, 2011. The tree is part of the city's "Sustainable Christmas" program that looks to raise awareness of energy consumption over the Christmas period. Visitors are invited to hop aboard a bicycle and pedal for as long as they like. The charge their cycling generates goes to batteries which store the energy for use when the crowd thins out and cyclists are few and far between. REUTERS/Imelda Medina (MEXICO - Tags: ENVIRONMENT SOCIETY)