Directions for creation of a steady eco-city (or an eco-district) and the criteria of stability and environmental friendliness of the cities are presented. The authors also recognize that the sustainable eco-friendly development of the city demands association of the matters of the so called "green" agenda and the "brown" agenda. On the other hand, there are places where the sharp social inequality and the interfaced social problems are presented. The authors prove that, although the economic activity of cities leads to serious environmental problems, cities have the greatest potential for developing ways of sustainable environmental development.