If I was to make my own city I would make sure it was always clean.  I would put areas around where you could recycle or reuse items.  Going along with that, I would encourage people to actually recycle and to maybe even reuse clothing, by adding thrift stores.  I would make sure that the electricity and power sources around my city were being controlled by renewable resources.  Some options would include, solar power and/or wind power.  I would make sure that everyone or at least most people would sign up for a day to clean the environment.  People would go around picking up trash and making sure we had plants planted all around.  I would also make sure that everyone would have a tech-free day at least twice a month.  This is so people can enjoy the outside and we could protect our air and water by keeping it from carbon produced by technology.  I would make sure that people had easy access to bikes and buses that they could take to work or school everyday.  Anot her thought would be to make sure we grow our own foods and keep habitats safe with parks and other natural resources.  I would want to make sure everyone had a part in keeping our community clean, healthy, and happy.

Those are good ideas. I like your idea of letting people sign up for a day to clean the environment.