Loring Air Force Base(300)Architecture for Humanity, the San Francisco–based nonprofit design firm that focuses on humanitarian projects, is soliciting designs for the adaptive use of closed, decommissioned, or soon-to-be abandoned military sites in its 2011 Open Architecture Challenge.

This year’s iteration of the biennial competition, [Un]restricted Access, asks architects and designers to envision the future of sites such as the Guantanamo Bay Detention Center, on Cuba’s southeast tip, and the Marine Corps Air Station, in Tustin, Calif. Participants also may add their own sites to the list, and have posted over a dozen so far, among them Spitbank Fort, a 19th-century garrison off the coast of Portsmouth, England, and a 16th-century bunker in Diefdijk, the Netherlands, used during the Eighty Years’ War.

In the U.S., there are currently 235 military sites scheduled for closing or redevelopment, many due to the 2005 Base Realignment and Closure act, which mandated that the Department of Defense downsize 5 percent of its infrastructure by Sept. 15 of this year. Among the structures slated to close is Fort Monroe—located on the southern tip of the Virginia peninsula—a Union Civil War stronghold that became a beacon for escaped slaves and may soon become a national park.

Other sites that the challenge’s entrants may redesign include the long-abandoned Cranston Street Armory, in Providence, R.I., which served as a recruitment center during World War II and a community center until 1981, and the Loring Air Force Base, near the Maine-Canadian border, which was closed in 1996.

For local economies, the closing of such bases means the divestment of millions in federal money, often accompanied by rising unemployment and urban blight. The competition hopes to generate ideas that will help bolster those failing economies. Cameron Sinclair, co-founder of Architecture for Humanity, said in a statement, “Through this competition we have the opportunity to create strong anchors in communities that will generate thousands of jobs and bring economic stability to those who surround these sites.”

Entrants can add a decommissioned site to Architecture for Humanity’s online map via Google Earth and Google Sketch. The deadline for submissions is May 1, with winners announced on June 29 and their designs exhibited next fall. In previous years, the competition challenged architects to design classrooms for the future and to create low-cost internet-access sites for the developing world.