David Sundberg/Esto

Cacti aren’t the only things growing in the Arizona desert. For nearly 40 years, an architectural experiment has been blossoming in the arid landscape 70 miles north of Phoenix with the goal of creating a sustainable alternative to urban sprawl.

Dubbed Arcosanti, the development is the brainchild of Italian architect Paolo Soleri, and its main purpose is to serve as a living exploration of Soleri’s concept of arcology, a philosophy that examines how architecture and ecology can harmoniously exist in compact urban environments.

The site is an educational venture where volunteers and students participate in workshops and construction from February through November. Over nearly 40 years, 6,000 workshop attendees have built 12 mixed-use buildings. Among them are office spaces, a visitor center, an amphitheater, a ceramic apse (above), residences, and greenhouses, not to mention a range of energy-focused experiments.

Many of the structures are constructed of poured-in-place and pre-cast concrete and are oriented to maximize solar energy and heat. Site plans call for five to seven acres of south-facing sloping greenhouses that act as the central food production system and also help harness energy. Although Arcosanti currently is connected to the grid, the American Hydrogen Association has devised a system that would use a solar-thermal conversion process to use sunlight to meet the entire project’s electricity needs. The plan features a dense complex of 40 solar-electric dish units similar in appearance to large satellite dishes that would each be capable of producing 35 kW of power per hour of sunlight. A backup system using water and stored hydrogen and oxygen would produce electricity at night and on cloudy days. The plan also includes a biomass conversion plant to convert the community’s organic matter, garbage, and sewage into hydrogen and carbon that could be used on site or sold as raw material.

One thing you won’t find many of on-site? Cars. Contrary to urban sprawl that encourages automobile use, Arcosanti’s master plan, called Arcosanti 5000, focuses on how compact planning can better conserve land, energy, and resources. When—or perhaps, if—completed, the pedestrian-friendly habitat is projected to house 5,000 people on only 25 acres of a 4,060-acre land preserve. Today, roughly 60 to 80 residents call the development home. To see how much is left to be built, as well as more details of the individual buildings and sustainable strategies, visit arcosanti.org.