Arcology is Paolo Soleri's concept of cities which embody the fusion of architecture with ecology. The arcology concept proposes a highly integrated and compact three-dimensional urban form that is the opposite of urban sprawl with its inherently wasteful consumption of land, energy, time and human resources. An arcology would need about two percent as much land as a typical city of similar population. Arcology eliminates the automobile from inside the city and reserves it for use outside the city. Walking would be the main form of transportation inside an arcology. The miniaturization of the city enables radical conservation of land, energy and resources. Arcology would rely as much as possible on the sun, the wind and other renewable energy so as to reduce pollution and dependence on fossil fuels. Arcology needs less energy per capita thus making recycling and the use of solar energy more feasible than in present cities.