A mural creates a secret garden at MIT

Made of epoxy terrazzo, a mix of colored epoxy and glass beads, Sol LeWitt's floor mural is hidden at MIT's Green Center. (George Bouret)

CAMBRIDGE - One of the remarkable works of art in Boston is hidden away like a secret in a new building at MIT.

The funny thing is, the building itself is hidden away too, surrounded on all sides by other buildings. Finding the work of art, therefore, is like opening a Chinese puzzle: a box inside a box inside a box . . .

The work of art is a floor mural by the celebrated American modernist Sol LeWitt. Hidden away as it is, it's like a secret garden. Even LeWitt himself never saw it. He died last April, at 78, only days before a contractor began constructing his mural from drawings.

In its obituary, The New York Times wrote of LeWitt that his "deceptively simple geometric sculptures and drawings and ecstatically colored and jazzy wall paintings established him as a lodestar of modern American art."

Ecstatic and jazzy the MIT mural is, but it's also rigorously ordered. He called it "Bars of Color within Squares (MIT)." It consists of 15 squares, each about 18 feet on a side. The squares line up to cover the floor of a corridor that runs around three sides of the ground level of the new building. The squares are divided geometrically and unpredictably into six or seven colors, and the colors are bright and intense. As far as I'm concerned, the effect is electrifying. You can't imagine this mural in any other location. The mural and the building lock together in a perfect marriage.

But it's more than that. MIT is an institution that does not have, conceptually, any outdoors. There are handsome quads and plazas, of course, but they always feel extraneous. They're not part of the DNA of MIT. The true public space at MIT is the famous "Infinite Corridor" grid that ties everything together. MIT, in other words, is organized as a system of (more or less) rigorous squares, inside which all kinds of crazy stuff goes on. LeWitt's mural, whether intentionally or not, reads as a depiction of the essence of this way of ordering the world.

You can walk on the mural. It's made of epoxy terrazzo, a mix of colored epoxy and glass beads, a standard flooring material for public spaces. You can see the mural better, though, if you hang out on any of the upper walkways and bridges, which look down like balconies on the mural below.

That brings us to the building, which is almost as satisfying as its mural. Designed by Payette Associates of Boston, it's called the Green Center. It's four floors high, tucked into what used to be a dreary service yard, surrounded on three sides by older four-story buildings and on a fourth by a low utility shed. Overhead is a glass canopy enclosing the entire space.

Building the Green in this cramped area must have been like building a ship in a bottle. But it works like a charm. The new building is set back 20 feet or so from the buildings on all sides, and it's that 20-foot strip that's floored by the mural. Above the mural, the 20-foot gap is just air and light, except where it's crossed by walkways that connect with the old buildings. Adjacent parts of these old buildings, too, have sometimes been renovated, so you don't have any clear sense of when you've moved out of the new and into the old.

What's interesting about the Green are the planning concepts it represents. They're the result of a master plan study done for MIT by Payette. MIT, of course, is at the cutting edge of science, which means two things. One, researchers from different disciplines want to interact with one another in unexpected and ever-changing ways. Two, there's a constant need for the latest technology.

In the famous Infinite Corridor grid, where do you put the often delicate and frequently changing equipment of new technologies? Where do you find space for social/intellectual interaction? It's grossly expensive and inefficient to carve out such places in the old buildings. Most universities, as Harvard is doing, and as MIT has done in the past with such buildings as the Stata Center, by Frank Gehry, simply build new buildings on the fringe of the campus. But Payette thought this approach would be like what happened to cities when the car came along: Everybody split for the roomier suburbs and the old center cities began to die. With new facilities sited at the perimeter, students and faculty would have to travel farther from the campus center to reach them.

Payette persuaded MIT that the way to expand was, yes, build new buildings, but build them not on the fringe but in the gaps between the old buildings. Densify MIT, don't let it sprawl. The Green is a thick pile of new technology and equipment, which is available to several different disciplines on three sides. The Green also offers something MIT has always been short of, namely casual lounge spaces for intellectual encounter (in each of those spaces, on a recent visit, was a chalkboard covered with math calculations).

Payette Associates, in the Green Center, is doing something thoughtful planners now say we should do with our towns and cities. We should mix many uses - living, working, shopping, recreating - close to one another in a denser city, the way MIT is mixing different sciences. That way, we wouldn't have to take a car to everything. We would be reducing the drain on the earth's resources and the pollution that generates global warming.

So the mural turns out to be a metaphor for MIT, and the Green Building, as a whole, is a metaphor for the future city. It's the kind of double shot of logic you associate with MIT.

Two addenda: the Green is Building 6C in MIT's peculiar mapping system. And the LeWitt mural, with its rare quality of color and finish, was built by DePaoli Mosaic of Boston.

Robert Campbell, the Globe's architecture critic, can be reached at camglobe@aol.com.