There are many different visions for regeneratively designed communities of various sizes & densities.
Arcologies, a fusion of Architecture and Ecology, were envisioned by Paolo Soleri in the 1960s and 70s as completely integrated megastructures, small cities in a single building of mammoth proportions. Living, working, shopping, agriculture, power generation, water purification, waste management and transportation were all woven together in a fully three-dimensional marvel of engineering and architecture. Everything was recycled, nothing went to waste. Passive solar heating and natural cooling strategies were often intrinsic to the overall form of the arcologies (apses to capture the warmth of the sun & ventilation cores hundreds of feet high).