Definition: A city designed with consideration for social, economic, environmental impact, as well as ingenuity and using resources to their greatest potential.
Example: Copenhagen, Denmark is considered one of the most sustainable cities in the world because of it's large amount of bike paths, high sensitivity to climate change, energy efficient buildings, and more. I chose to put sustainable cities in the urban planning category due to the fact that creating a sustainable city requires a lot of careful and thoughtful urban planning.