NESTLED in a small tract of land off Francis Ave. behind the Biology Labs and in front of the Divinity School sits Harvard's strangest building. Outside, in the shadow of the labs, a little mob of preschool children are running around a makeshift, fenced-in playground. "YARD RULES," a nearby sign reads: "Smacking the windows is not allowed. Sand stays in the sandbox and off the slide...."

One floor above them, in a large, dark laboratory, works a team of archaeologists, scraping the dirt off a pile of shards and filing various artifacts into hundreds of cardboard boxes that line an entire wall. "This place is conducive to doing work that has no real theme to it," says one. "Accessibility is pretty important too," adds another. "We work pretty odd hours."

The corridors inside are long, green and dimly lit; the walls are bare except for a spray of handwritten signs and arrows and random words scrawled on them, often in several handwritings. One of these appears every few yards: "Polish, Hebrew, Chinese." "Sufism, Hebrew, Polish, Czech." "Polish, Chinese, Hebrew, Tech Writing." "Turkish in 6 Divinity."

At the end of one stark hallway two women speak in Japanese. "Alistair Cooke," one of them asserts. The other sprinkles her reply with English words: "...diction...delivery...."

On a table in the middle of another hall lies a pile of mail, all addressed to Vanserg Hall. The letters are earmarked for "Mining and Metallurgy Lab." "Project for Kibbutz Studies," and assorted economists, among others.

An index card on the door of one third-floor office identifies the occupant as Daniel B. Hogan, Psychology and Social Relations. Above the door, a note reads "Professor of Military Science" in large painted lettering.

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VANSERG HALL was hastily built in 1943 by the U.S. Office of Scientific Research and Development as a radar laboratory. The architectural firm of Coolidge, Shepley, Bullfinch and Abbott, which under one name or another designed all the River Houses, departed from the neo-Georgian elegance that characterized their earlier work for Harvard and put together a plain three-story structure with a flat roof and red shingles.

Three years later, when the war was over. Harvard made this homely compound an unlikely addition to its collection of historic and innovative buildings. Harvard students have been hiking to Vanserg (and getting lost on the way) ever since.

The building has served a number of functions over the years, the most notorious of which has been its stint as headquarters, with adjacent Shannon Hall, for Harvard's Reserve Officer Training Corps (ROTC). That program came to a turbulent end in 1969, when anti-war student activists occupied University Hall and led a subsequent student strike, calling for a list of demands that included removing ROTC from the campus.

After the military program's banishment, Vanserg moved into its current phase, serving as a sort of refugee camp for misfit classes and offices. The registrar's office assigns classes to Vanserg only as a last resort, after all other University rooms are booked. This fall, inordinate numbers of students have classes there: portions of the building were subdivided and refurbished to ease the classroom shortage that renovations in Sever Hall brought on. The classes relocated, though, are still the usual Vanserg rag-bag of offerings from all corners of the Faculty.

Vanserg's offices are uniquely responsible for the hall's bizarre character: they are strewn about the building with all the order of shrapnel in a minefield.

The bottom floor belongs in great part to the Harvard Yard Day Care Center, a University-affiliated nursery for children from 18 months to five years old: most of the clientele are children of Harvard faculty, staff, and students (Another similar center can be found in adjacent Shannon Hall.) The center has all the familiar hallmarks: awkward drawings of rainbows boxes labelled "Beans & Seeds," coats hung by their hoods on hip-high hangers. All around, toddlers run and scream, even, on occasion, wandering into calculus sections or Japanese lectures going on upstairs.

The balance of the first floor is used as studio space by the Visual and Environmental Studies Department. Upstairs are several long hallways' worth of small offices. The University piano tuner has one, so do about a dozen teachers in the East Asian Languages and Civilization Department. At one end of the floor is the Project for Kibbutz Studies, a branch of the Center for Jewish Studies that coordinates research and teaching on Israeli cooperative communities.

AT ANOTHER end lies the Institute for Conservation Archeology, a branch of the Peabody Museum that sends staff members to tag along on various construction sites in the area, observing and collecting the constructions and artifacts that emerge. (All federally funded construction projects are required to retain conservation archeologists.) The institute's staff is liable to come upon anything ranging from prehistoric rock shelters to 19th-century pottery to preserved bones.

The third floor features, along with scattered Economics and Government Department offices, the Harvard Hillel Children's School. Outside, the hallways are crowded with carefully handwritten book reports, stars-of-David made of popsicle sticks, and posters that say "Have you hugged your Hebrew book today?"

A few doors down is the headquarters for the CUE guide, the official, student-run advice book on undergraduate courses. The office is sparse--the guide does most of its work in the summer--but the computer terminal inside is still humming and the file cabinets are full. Considering the rest of the building, it is no surprise that these cabinets were issued by the U.S. Army no one knows how many years ago, and that they have U.S. serial numbers stamped on top.