All cities have one key resource: the special abilities of the people who live in them. You just have to find out what they are. In the Australian city of Adelaide, for example, which is overshadowed by Sydney and Melbourne, I discovered a number of experts in the penal system. I advised them to work with these special skills.

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.

As far as population size goes, big is no longer important, and it can even be a drawback. In fact, the future belongs more to second-tier cities. Any place can become a world-class center today by finding an area in which it outperforms others, by thinking for the long term, by expanding its competitive abilities and by operating globally.

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.

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.

Another thing I like about German cities - and it's an advantage which they haven't sufficiently exploited yet - is that they are pioneers when it comes to environmental technologies. And green solutions are becoming more and more important.

Some remain great cities, but they shouldn't stand still. They should move in the direction of a knowledge-oriented society. Most cities have to do something to draw attention to themselves and make their particular assets visible on the international radar. I'm not talking about developing countries, but about the United States and Europe.