Arcosanti is the urban laboratory that Italian architect Paolo Soleri (1919-2013) started in the 1970s. This prototype of a large town, standing in the desert of Arizona, is under development by a community of volunteers and employees, and can be seen via a guided tour. The key idea is to minimise urban sprawl and save resources for ecological reasons. A few buildings, including homes, a shop, a café and a lecture hall, are already operational.