The office-shopping boomtown--boomcity? boomsuburb? -- at Tysons Corner is distinguished for the amount of construction being done, for the amount of money being spent (on everything from build- ings to a cornucopia of consumer goods) and for the number of cars that crowd its roads.

But the place is distinctly -- even memorably -- notable for the absence of excellence in its architecture. If there are a few new office structures of more than modest esthetic merit, their effects are largely lost in an overall pattern of buildings that range from boring to bad and back again.

Last Wednesday, however, with great fanfare -- Gov. Charles Robb was there, along with assorted local politicians and many of the bankers and developers whose investments are transforming the Fairfax County landscape -- ground was officially broken for the first of three new office towers that without question will help give Tysons a striking new architectural image.

These mirror-image brick buildings, with their odd, astonishing columns and rooftop arches, were designed with imaginative e'clat by Philip Johnson and John Burgee of New York, architects whose names in recent years have become synonymous with highly visible, unusually controversial and generally excellent projects. Johnson, 78, is probably the most famous architect in the country. His collaboration with Burgee, 51, began 17 years ago. Most of their biggest and best buildings, in cities throughout the United States, have been designed during the last decade.

The fact that the Johnson-Burgee team did well for Tysons (and for James T. Lewis and Richard M. Patrick of Tycon Developers) is fortunate, for the new buildings -- even if they were bad or indifferent as architecture -- inescapably would alter the local skyline. Each will provide nearly half a million square feet of office space, and each will rise 230 feet. This is hardly tall by non-Washington standards, but, as Lewis proudly points out, it is higher above sea level than the tower of the Washington Cathedral, the highest built spot in the city.

Johnson, in his usual sparkling form before the groundbreaking on Wednesday, explained that the firm accepted the job because "it was a challenge we couldn't possibly turn down, a chance to build on one of the great sites of the world, so high up over Washington." He also said that "building here in Virginia, we couldn't help but feel Mr. Jefferson looking over our shoulder."

Suburban, Virginian, Jeffersonian touches do indeed enliven the design, starting with the graceful way the buildings are placed around a curved, grassy open space. It is not at all hard to imagine, as a mental image behind this plan, the idea of Jefferson's Lawn at the University of Virginia, with its Palladian pavilions rising at regular intervals on the edges of the green campus. Nor is it preposterous to compare (as Burgee did) the grassy Tycon court to the typical suburban "front yard." In each case the buildings define the space, while the space sets off the buildings.

Such associations, employed as here with intelligence and skill, help give meaning to architecture. Their absence in most of the new buildings in Tysons helps to explain the glitzy bleakness of its visual environment. But clearly, Johnson and Burgee are not playing the revivalist game. The buildings are big and their use is contemporary and, accordingly, the design invokes history with an outsized flair.

The new towers are almost exactly alike in shape and size (the centerpiece being slightly wider than the flanking buildings). Each is concave in front and convex in back. Otherwise front and rear are indistinguishable, in fitting recognition that in this automobile-oriented, non-urban environment most people will enter and leave the buildings from the back, where the cars are parked, while most will perceive them from the front, where the cars drive by.

Each fac,ade, true to classical antecedents, is symmetrically organized. At the center of each is a three-story entrance portico, in itself a tidbit of Jeffersonian-Roman design, that serves as a base for four colossal brick-sheathed columns rising 176 feet to culminate in two giant arches, one set within the other.

At this point, with the buildings visible only in model form, it is hard to tell just what the final effect of these remarkable colonnades will be. So far as I know, they are far bigger than anything actually built in the ancient or Renaissance worlds. (The only actual columns I know that compare are Montgomery Meigs', in the Old Pension Building in downtown Washington.)

But even if they turn out not to be wholly satisfying in the old ways, they are a rich, daring piece of design that responds to the scale, and in a way to the oddball, anything-goes architectural context, of the new Tysons Corner. Johnson and Burgee took the ironies of their site in good humor: Besides defining that attractive open space, their buildings, set back from Leesburg Pike, form a sculptural envelope for an existing, and typically banal, Marriott Hotel building. It just may be the handsomest suburban setting any Marriott has ever received.

Then, too, the colonnades and arches are not simply tacked onto otherwise bare-bones contemporary office structures. One of the more appealing facets of the fac,ade designs is their thoroughgoing integration: the columns at once extend and interrupt the march of brick-sheathed half columns that give the fac,ades needed depth; the arches emphasize the Sullivanesque horizontal division of the buildings into base, shaft and crown; and these divisions themselves are reflected in skillful changes of window pattern at each level.

The handling of scale in the middle windows, where two stories are disguised as one, is particularly skillful. This contributes in no small way to the compact impression the buildings will make, and it creates a strong horizontal foil for the soaring verticality of the central colonnades.

Something should be said as well for another ingenious feature of the site plan. Insofar as a seven-story garage for 4,000-plus cars can be hidden, this one is. The enormous building was tucked into the slope of a hillside so that where it faces the buildings in a gentle arc it is but a pleasant two-story structure. It was "designed out," as they say, on all sides. (The developer deserves much of the credit here -- there was no skimping on external materials. What the structure will be like on the inside is another question.)

The Johnson-Burgee firm designed the Terrace Theater inside the Kennedy Center. Johnson himself is responsible for the David Lloyd Kreeger mansion on Foxhall Road, and the geometric jewel that houses the pre-Columbian collection at Dumbarton Oaks. The new project, to be built in stages, with the first building slated for completion in 1986, is the firm's first large-scale effort in the Washington area. It is by any measure a welcome debut.