Today, more than half the world’s population lives in cities. By 2050, the figure will have risen to more than two thirds. Cities produce huge amounts of greenhouse gases and garbage, and are at the root of many of the world’s environmental problems. Energy, water and raw materials are in increasingly short supply. What can we do to halt this trend? The series Ecopia looks at exciting projects that address key questions: How should we live and work in the future? How should we shape our public urban spaces? How can green architecture provide new impetus for urgently needed ecological reforms? The first three programs present examples of innovative projects and developments in ecological architecture and urban planning. 01 Eco-Cities Hamburg’s Hafencity and the Tianjin Eco-City have been praised as models of sustainable urban planning. A huge stretch of derelict dockland along the Elbe river in Hamburg is being redeveloped to create vibrant new city neighbourhoods. It is currently Europe‘s largest building site. The Tianjin Eco-City in eastern China is being built on undeveloped land. The plan is to try out eco-friendly technologies that can help slash energy consumption in China‘s cities. 02 Worlds of Knowledge School buildings made of locally-sourced clay in Burkina Faso, with a sophisticated roof construction and a passive ventilation system that uses no electricity. A university campus in South Korea that has been partially sunk into the ground to blend in with the landscape of an existing park. And a virtually planned science lab in Germany that is carrying out research into work environments of the future. These three sustainable projects from Africa, Asia and Europe in the education sector invite imitation. 03 Sports Worlds The organizing committee says London 2012 will be the most sustainable Olympic Games of all time. The critics say that such extravagant and expensive architecture designed for limited usage cannot be considered sustainable. The planners say it can and point to the energy-efficient Velodrome, which was built using light-weight materials and relatively little energy, and the Aquatics Centre, which can be remodeled for future use. In the Brazilian city of Manaus, one of the world’s first ecologically certified soccer stadiums is being built for the 2014 Soccer World Cup. Ecological principles are of uppermost priority in the choice of site, the construction process, water management and energy consumption.