The world is increasingly urbanized.  The urban population has practically doubled in the last 20 years. For this reason, I think it is better to invest now in large cities and megalopolis. Indeed, large cities offer enormous possibilities to reduce pollution and to modify the global impact. I have read that some organization, like the WWF, give awards to cities who develop the best programs to make the future more renewable and livable.

Yes, I agree with you and I think you're right. Urbanization and the consequent growth of large cities are growing more and more nowadays. At school we have learned that this process began at the beginning of the twentieth century thanks to the development of industries in large cities. In the meantime, pollution and other negative consequences for the environment are also increasing thanks to the phenomenon of urbanization. According to a study by ISPRA (Institute for Environmental Protection and Research in Italy), the soil consumed from the 1950s to the present day amounts to 7% of the Italian surface area. Considering that the towns are one of the main causes of pollution, I believe it is appropriate to intervene primarily in large cities. I've heard about the initiatives of the WWF too, and I think that is a great idea. Today there is a big amount of   “sustainable city projects” which are presenting different solutions. An interesting example could be the “CityTree” designed by a Berlin start-up. It is a tree that would have the ability to filter the air. On the on e hand, this project could reduce pollution, on the other hand it would also partly solve the problem of the lack of green spaces in cities.

Yes, I agree with both of you, but I believe that the criterion for a completely ecological city should not be the size of this city, but the fact that it uses 100% renewable technologies. Is it worse to live in a small town without renewable resources or in a big town with all renewable resource?