Asked for projects that could solve major social or economic problems or make government more effective, the cities "stepped up with bold and creative ideas," Bloomberg said in a statement. Several European finalists looked to technology's potential to improve residents' lives: auditory alerts to help blind people get around Warsaw, Poland; new systems for Londoners to monitor their health; and methods for making energy out of the heat thrown off by Madrid's underground infrastructure, for example. Barcelona aims to make aging less lonely through social networking the old-fashioned way: identifying a team of relatives, friends, social workers and volunteers for each elderly person. The Welsh city of Cardiff intends to help residents take small steps to be more productive, the Dutch capital of the Hague is proposing to let citizens choose how part of their taxes will be spent, and Stockholm wants to get people producing biochar, an organic, charcoal-like material that can improve soil quality and purify water, among other environmental benefits.