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.

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.

Contradictions, most of all, a balance between chaos and order. It needs neighborhoods vibrating with energy just as much as cozy little corners and parks; well-tended, middle-class sections as well as an alternative scene; technology centers for innovative youth and social facilities for older people.

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.

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.

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.