The Guggenheim of Bilbao, now 20 years old, is perhaps the most influential building of the latest two decades, not so much because it is Frank Gehry’s greatest work but because it represents a way of transforming and activating the image of cities that we associate with the building’s name: the ‘Guggenheim effect.’ The ‘icon’ trend that was set off by Bilbao has been much delegitimized since, but Gehry’s Guggenheim does show that with good planning and management, iconic architecture can still be a weapon loaded with future.