Building on HafenCity's success, the German city of Hamburg reinvents its Elbe Islands as a test bed for innovative and experimental mixed-use projects. This article first appeared on GreenSource. The "Building Exhibition within the Building Exhibition" is home to 18 futuristic housing complexes. In 2007 the International Building Exhibition (IBA) Hamburg – a real-time urban research and development laboratory – began to shine its spotlight on the city’s Wilhelmsburg district, the world’s largest inhabited river island outside Manhattan. IBA Hamburg follows the unmitigated, mixed-used triumph of Hamburg’s HafenCity. Ten years ago HafenCity was an abandoned port and industrial center, wasting