It's known as 'Mad City,' but Wisconsin's state capital is a mecca of eco-friendliness, from its 100 miles of bike paths to its locally owned downtown shops.
Motown may be broken down, but locals have the rare chance to reinvent their city from the ground up. Can Detroit become a city known for its bikes, trains and farms?
The biggest city in China is quickly becoming one of the greenest, and it's using the 2010 World Expo to morph into a global example of sustainable and harmonious living.