You probably know what the main terminal building at Dulles International Airport looks like. You also may know that the Dulles terminal is among America's best-known works of architecture, designed in the 1950s by Eero Saarinen, son of acclaimed Finnish architect Eliel Saarinen.

But what you may not know is that Eero Saarinen, unlike many notable modern architects, did not develop nor relentlessly advocate a singular, formulaic, personal style. Saarinen's buildings do not look alike.

You can readily identify the signature work of American architects Richard Meier or Frank Gehry, Spanish architect and engineer Santiago Calatrava, Japanese architect Tadao Ando or Iraq-born British architect Zaha Hadid. Each of these designers has a way of composing building geometry, structure and space, typically with a preferred palette of materials, details and colors. By repeating or slightly varying memorable elements, they create instantly recognizable projects, no matter what or where the project is.

By contrast, Saarinen stands separately partly because of his commitment to treating each project differently. He believed that objectively definable project circumstances -- site, climate, functional needs, cultural context, client characteristics, technological and economic resources -- required original thinking. He consciously resisted the prevailing dogma of 20th century modernism and the International Style, the belief in promulgating a universal architectural language.

Although Saarinen was always interested in innovative structural systems and materials, his work is diverse in its compositional and structural approach and in its expressive, metaphoric allusions. He could be simultaneously rational and romantic.

For his first large commission after World War II, the General Motors Technical Center outside Detroit, he created a campus of contrasting structures grouped around an artificial lake: rectilinear, low-rise research buildings; a dome-roofed assembly building; and a tall water tower standing in the lake. He clad the research buildings with glass and metal curtain walls, adopting for the first time neoprene glazing gaskets similar to those used for automobile windshields.

In his view, this was the logical, appropriately expressive architectural vocabulary for a research facility belonging to an industrial corporation whose assembly lines manufactured streamlined products.

Saarinen's designs for other corporate facilities -- John Deere, IBM, Bell Laboratories, CBS -- continued using evolving curtain wall technologies. But in each case, he explored new compositional tactics, details and finishes -- such as permanently rusted rather than painted or galvanized steel -- for making building skins with metal and glass.

Metal and glass curtain walls became the signature hallmarks not of Saarinen, but rather of his well-known contemporaries, Ludwig Mies van der Rohe, Philip Johnson and Skidmore Owings & Merrill.

At the Massachusetts Institute of Technology in the 1950s, Saarinen designed Kresge Auditorium, considered a structural tour de force not because of its skin, but because of its roof, an ultra-thin, spherical concrete shell resting on only three points. Standing a few dozen yards away from the auditorium is the structurally simple but spatially lyrical MIT Chapel, a flat-roofed, skylit cylinder faced with red brick and surrounded by a shallow, circular moat. Saarinen's chapel is a counterpoint to the larger auditorium dome.

At Yale University, searching for more ways to dramatically span large spaces, he designed the David S. Ingalls Hockey Rink with a roof supported by a reinforced concrete spine that arches lengthwise over the entire hockey rink. The roof surfaces are then suspended laterally between the spinal arch and lower side walls varying in height. The resulting curvilinear form resembles a whale -- an unintended metaphor -- and engendered the building's nickname, the Yale Whale.

Yet Yale's many neo-Gothic edifices led Saarinen to fashion for the university a new dormitory complex -- the Ezra Stiles and Samuel F. B. Morse Colleges -- that could not have been more unlike the hockey rink. A tight, bending cluster of low-rise, faceted buildings is clad entirely in randomly patterned, rough-hewn limestone with narrow, vertically proportioned windows. They were clearly inspired by and meant to evoke a medieval village.

Dulles's suspended, seemingly hovering roof recalls an inverted aircraft wing and sweeps your view skyward. Its cousin, Saarinen's TWA Terminal Building at New York's Kennedy Airport, looks like a mythical bird, hovering with its curving, outstretched wings sheltering the concourse below. Both terminals were explorations of the use of thin-shell concrete technology to shape metaphorically expressive yet functional structures.

The soaring Gateway Arch overlooking the Mississippi River in St. Louis was designed early in Saarinen's career, as part of a competition. But it was completed only after he died in 1961 at age 51. It is yet another tour de force, not because of its shape -- the arch is an ancient structural form -- but rather because of its great height, thin proportions and method of construction.

Many architects reject the search for a new form for each new project that characterized Saarinen's practice. Instead, they fall in love with and nurture a particular stylistic language. This usually occurs early in their careers. Such architects see themselves primarily as dedicated artists, motivated in part by a desire to differentiate their work from the work of others, just as sculptors, painters, poets and writers might.

Embracing and avidly pursuing a signature style is not inherently a good or bad way to practice architecture. But it can be problematic if the stylistic language becomes overly immutable and formulaic, if it makes little sense for the circumstances of a particular project, or if it yields buildings whose structural and aesthetic durability prove to be short-lived.

Throughout his architectural quest, Saarinen clearly understood this, and for those architects continuing the quest, he remains a worthy role model.

Roger K. Lewis is a practicing architect and a professor of architecture at the University of Maryland.