In a city like London, the fact that cultures live together and cross-fertilize is a beautiful and natural thing. The many cultures in Amsterdam contribute to the city's high level of craziness - something which every interesting city should offer. But sometimes immigrants can live in parallel worlds which can exclude others and not be very attractive.

The Germans are often too bureaucratic, too fixated on rules and not risk-oriented enough. And some of their officials have the feeling that they need to make everything in the cityscape look nice and pretty as quickly as possible. That was particularly apparent in the former East Germany after reunification. Then cities sometimes get a bit too neat and tidy.

Creativity cannot be really regulated, but it can be encouraged. The redevelopment or revitalization of a city is an art. It depends on the individual strengths of a place and the will of the leadership to bring about change. The goal is to establish a cultural infrastructure.

Hamburg is getting a new symbol with its new Elbe Philharmonic concert hall. Such an architecturally impressive building is built somewhere in the world maybe once every five years, if you're lucky.

Detroit is an urban hell. But even in this city of the dying auto industry, there is reason to hope, if they manage to combine the creative forces of designers and other intellectual "suppliers" in other ways.

City needs creativity to retain the high performers who have lived there for years as well as to attract new, interesting residents.

I like what Barcelona is doing. This city almost perfectly combines its natural advantages with cultural attractions, IT parks and first-rate educational opportunities. The same applies for Dublin, which manages to achieve a blend of complexity, tolerance and artistry and makes a point of not devoting every part of the city to the tourism industry. Sometimes creativity also means forgoing short-term profits and simply saying no.