The startling success of the city's plan to turn the Franklin Park area into a trouble-free zone of prestige office buildings is symbolized by the recently completed building on I Street NW at the park's southeastern edge. Actually, it is enshrined there.

This is one classy quasi-classical building, from polished black granite base to elegantly scalloped green-tinted roof. The proportioning is exact, the detailing adept, the materials fine, the craftsmanship exemplary. The lobby is stupendously quiet -- the click of a heel on its patterned marble floor is an event.

Designed by the powerhouse New York firm of John Burgee Architects With Philip Johnson for the powerhouse Texas development company Gerald D. Hines Interests, the building is everything the client could have asked for. It is a big, efficient Washington office box dressed up grandly.

Pritzker Architecture Prize laureate Johnson, the principal designer, obviously had Washington traditions of monumentality and classical architecture in mind -- the building is as concise a reprise as one could imagine, a succinct reminder of the kinds of official and commercial buildings facing green squares that the McMillan Commission advocated so memorably in its famous report of 1901.

And yet, typical of the firm's nationwide efforts of the 1980s -- is there now a self-respecting American city without its piece of Burgee-Johnson postmodernism? -- this building is at once an abstraction and an exaggeration of traditional motifs. Regardless of the stylistic inspiration -- Victorian, classical, whatever -- the Burgee-Johnson designs are all simple diagrams, but this one is a lot better than most. One gets the feeling that the built-in limitations of the Washington box were a help -- with height and bulk so rigidly prescribed, the architects simply made the best of it.

The primary feature of the main facade, fronting the park, is a long row of limestone-sheathed piers attenuated in the manner of the stripped classicism that was used in the 1930s for both authoritarian (in Berlin) and democratic (in Washington) ends. There's a touch of genius here -- to appreciate its efficacy one only has to compare this colonnade to the pathetically starved version at the Madison Building of the Library of Congress or, contrariwise, to the grossly inflated columns adorning several recent office buildings downtown.

The colonnade is beautifully framed. Stretching from the ground to the 11th floor, the narrow piers are exciting in their vertical thrust, which is fittingly counterbalanced by the balustraded 12th floor and the splendid roof. The building's stone-coursed corners, too, are appropriately hefty in feel. The piers themselves punctuate a terrific curtain wall that helps to counteract their verticality.

It is amazing how much glass there actually is in this "stone" building. It's also very pleasing to see the improbable ease with which this pattern -- clear glass windows, simple cross-mullions, light gray frames, light blue-green vertical struts and dull gray metal spandrels -- manages to combine the best of three worlds. There's a sleek suggestion of the International Style, an elegant whiff of Washington's stripped classicism and a handsome touch of the Beaux-Arts spirit.

This is, in other words, a harmonious composition in which every piece, from rooftop ornament to balusters to mullions to canopies to ground-floor lanterns, seems justly proportioned in relation to the whole.

Gears switch in the lobby, a more or less erudite recall of temples and, more to the point, of bank lobbies past. The limestone Doric columns -- flutes, entasis and all -- are things of beauty, and it's an altogether impressive if none-too-friendly room, from coffered back-lighted ceiling three stories high to lozenge-studded wall to polished marble floor. Betty Rood, a vivacious security guard who recently moved to Washington, reports that lots of architects have been stopping by for a look. "I'm from Chicago," she says, "so I'm used to it."

There's a flaw in the blissful picture, of course. In a way the Franklin Park story is a model of how the planning process is supposed to work -- in the public interest the government establishes goals, and, properly assisted and guided, private enterprise follows through -- but dullness of a certain kind is a predictable result.

The park itself, though still somewhat the worse for wear, remains one of downtown's biggest and most commodious islands of green. But the surround of new buildings (and excepting the picturesque Franklin School and the Beaux-Arts Hamilton building, they're all new) sorely misses customary signs of urban vitality -- interesting stores, places to eat, night life, color, signs. The place is becoming so homogeneous one soon may need a briefcase as a ticket to get in. And that's during the business day. Nighttimes, forget it.

This isn't altogether a disaster. Downtown's main shopping district is but a few blocks away, after all, and it does make all sorts of sense for the city to create an environment attractive to high-priced law firms, corporations and the like. This was the point of mapping out the Franklin Park area as a prestige office district in the city's comprehensive plan.

But relentless single-use zoning begets a relentless single use when that use is office space. What the city asked developers to do in this area is what most downtown developers would do automatically, if left alone: demolish anything left standing from an earlier era, cover the lots with full-envelope office buildings and leave the rest to chance (or, if you prefer, to the invisible operations of the marketplace). It's a disease that often spreads -- there's at least one application pending from a developer who wants to forgo residential requirements on a nearby site in favor of offices. The justification? Why natch, it's all those single-use buildings around Franklin Park.

There's also the probability that the Franklin Square Association, a group of developers, bankers and tenants, suffers from a certain overzealous mind-set where retail uses are concerned. Fantastically upscale shops would be fine, of course, but when these folks think downscale they think for sure of the sex bars and porno emporiums that made up the 14th Street strip, which they fought hard and successfully to eliminate. It's a shame, looking at 14th Street today -- there's almost nothing there -- to recall that the buildings that housed this tawdry lot were at one time occupied by a vibrant assortment of more respectable places of business and entertainment.

It is interesting, if unsurprising, to see how the new architecture reflects the single-use mentality -- the buildings tend to be at their worst at ground level. Johnson's building is a chief offender -- its polished black granite base at the corner of 13th and I streets is taller than most passersby, and its 13th Street facade, given over to garage and alley entrances, deadens a once lively city street. Even its handsomely designed, canopied storefronts, facing the park, offer minimal attraction. There's a branch bank in one. Soon to occupy another entire set will be the members-only Club at Franklin Square. One presumes the club was formed at least in part out of dire necessity -- where else to eat?

It should be pointed out on a somewhat happier note that one of the two small businesses in the lobby of this building -- they're kept tastefully out of sight -- is the cozy shop of George Obusek, an expert repairer of watches and clocks who's been downtown for more than three decades, mostly in a now-demolished building near Gallery Place that used to house more than 20 jewelers and jewelry-related businesses. Obusek has been a gypsy of late, keeping just ahead of the wrecking ball until, he says, he "got to know the Hines boys and they made me an offer with this place."

Obusek's store is an adornment of an unfortunately diminishing kind. The building it is in is an adornment of another order. Together with its contrasting companion piece on the west side of the block -- an attractive, semi-flashy clock tower building designed by the Weihe Partnership for Manufacturers Real Estate in a modernistic commercial vernacular -- it establishes a satisfying sense of enclosure when seen from the spacious, leafy park. Yet it remains a singular and in some ways even a thrilling piece of architecture.