Last month, Circuit City announced that it would close 155 of its stores, most of them big boxes: those 50,000- to almost 300,000-square-foot warehouse-like structures, often built far from city centers. By one estimate, there are almost 3,000 vacant big boxes littering the American landscape, with more to come as major retailers falter. Makes Wal-Mart’s logo, that “Always” emblazoned on their façades, seem ironic: what’s really permanent is the big box as retail grave.

The environmental impacts of big box stores are well documented — among other things, they consume green space, encourage driving, and soak up public funds. But what happens when they shut their doors?

Often a municipality has put in new roads and electric lines — what Julia Christensen, author of Big Box Reuse, calls “corporate-specific infrastructure” — to coax a big box like Wal-Mart to come. When the company abandons the original store — whether to downsize operations or, in some cases, to move on to an even bigger facility — it leaves a big-box carcass. These hulking structures are poor candidates for “adaptive reuse.”

“The challenge is size,” says Christensen. “It really is hard to find an institution that uses 200,000 square feet of space, and since they’re built for single purposes they’re hard to use for multi-purposes.” The easiest reuse for a big box is another big box, and that’s not always allowed. Wal-Mart, which maintains a whole separate company, Wal-Mart Realty, to handle its 1,000 or so empty stores (and encourage development around them) often inserts a clause into contracts that no competing company can occupy the property. “You can bet a Wal-Mart building will never be a K-Mart building,” Christensen says.

So what will it become? Christensen has spent years seeking out and documenting reborn big boxes, those rare adaptive reuses; so far she’s found about 35. A Wal-Mart in Round, Rock, Tex., became an indoor raceway. Another Wal-Mart transformed into a senior center in Wisconsin Rapids. A Hastings, Neb., K-Mart turned into a Head Start. In Austin, Minn., the old K-Mart was reconfigured as the Museum of Spam.

The most common reuse Christensen found in her (admittedly un-empirical) research was charter school, which tells us something about the dire need for school construction. But more surprising than the number and kinds of reuses was the attitude of those who inhabited the revived spaces. “Across the board, there was a sense of joy and excitement about turning something like that into a community space — this sense of ‘look at what we did,'” she says. Teachers joked that they taught in the cheese section; students ate lunch in the electronics aisle.

But Stacy Mitchell, author of Big-Box Swindle: The True Cost of Mega-Retailers and the Fight for America’s Independent Businesses, thinks reuse might not be the answer. “Most of these buildings are pretty cheaply constructed, not made to last a century,” she says; in her opinion, razing and rebuilding is a better use of space. “The ideal situation is that these sites are redeveloped completely as multistory properties, and that the building isn’t saved.”

That, of course, presents another environmental problem. As Christensen says, “What kind of landfill do we have that 3,000 empty big box buildings can go into?”

Reuse or raze, the real issue is the overbuilding that led to so many millions of square feet of abandoned, difficult-to-reinvent space in the first place: too many big boxes, and too-big big boxes, built too far away. Mitchell says there were 19 square feet of retail space per person in the U.S. in 1990; by 2005, that number had doubled, but spending per person went up only 14 percent. We made far more retail space than we can use.

Luckily, we’re beginning to learn from our mistakes. Towns are adopting big box ordinances, some of them banning big boxes or insisting that they have broken-up facades, so it looks like many stores instead of one, making it easier to reuse. Some municipalities require a developer to pay for future demolition, should the property become vacant. Says Christensen, “They’re going to take design decisions into their own hands, and not accept these corporate homogeneous structures over and over again.”

Meanwhile, there could be as many as 3,000 empty stores out there, waiting for their next incarnation. What do you think your local big box should become?