According to the Arcosanti website:
Arcosanti is an urban laboratory focused on innovative design, community, and environmental accountability. Our goal is to actively pursue lean alternatives to urban sprawl based on Paolo Soleri’s theory of compact city design, Arcology (architecture + ecology).
Built by over 7,000 volunteers since the commencement of the project in 1970, Arcosanti provides various mixed-use buildings and public spaces where people live, work, visit, and participate in educational and cultural programs.
The project’s leader, Paolo Soleri who died earlier this year, called Arcosanti “optimism in concrete.”