Why is sustainability important in today's world? What is sustainability? We look at cities specifically at and how they are planning to be more sustainable in the 21st century. There is a big difference in renewable and nonrenewable resources and how long they will last. What can we do to be sustainable? There are examples of mixed-land use, walkability, and transportation-oriented development. We also look at smart-growth and how cities are using new urbanism, green belts, and slow-growth to become more sustainable. We also look at the benefits and detriments of urban design. Lastly, we test your knowledge of sustainability with some MCQs taken directly from the AP Classroom website!