There is a new city in Washington. Located in historic Georgetown but not really of it, spilling precipitously down the hill between M Street and the Potomac River, this city has appeared with amazing -- some would say alarming -- suddeness, even though it has been coming our way for nearly a decade.

Two recent events, in addition to the continuous drone of construction in the area, have centered attention upon its existence, which is surprising, inescapable, problematic and promising all at once.

One is the opening of Georgetown Park, the neo-Victorian concoction of luxury shopping mall and condominiums that has lured the curious in traffic-jam proportions to the M Street border zone between the old and new Georgetowns.

The other is the District government's decision last week to look with favor upon a $154 million office-commercial-residential complex on 3 1/2 acres of privately owned Georgetown waterfront property.

The two developments present striking contrasts. In its glass-canopied interior, Georgetown Park certainly satisfies the contemporary architectural sweet tooth. But it has created an impressive (and predictable) problem of automobile congestion, and it feeds nagging doubts about the residential mix in the new Georgetown south of M Street.

The long-debated waterfront project, on the other hand, is a circular, colonnaded eccentricity. It is a strong, positive statement about the way the city can meet the riverside in happy civility. By introducing boats, trees, shops and restaurants close to the waterfront, the project will invite people to the water's edge, give them things to see and do there, and tempt them to stay into the evening.

Both projects, however, underline the main point. This new Georgetown is so different from the old in look, scale, style and use that it hardly makes sense any longer to speak of them as the same entity. The Georgetown of tree-lined streets and low-lying residential rows essentially stops at M Street. Beyond M begins the Georgetown of massive brick office buildings, stacked condominium units, labyrinthine walkways, bricked courtyards and stores secreted in every improbable cranny.

One suspects that the two places -- one a residential neighborhood, the other an urban agglomeration -- will learn to live together, but the friction between the two is palpable. More than ever M Street today has the look, and the beleaguered vitality, of a high-rent honky-tonk strip. Neighborhood service stores have been forced out by excessive rises in property values. A nimbus of transient prosperity floats about their chic, or chic-shabby, replacements.

And yet the new city down the hill is there and it won't go away. If it clearly is not the blessed dawn of a "gracious, sophisticated new in-town life style" that its developers tout, neither is it the unabating catastrophe that preservationists and the Georgetown Citizens Association bemoan. Perhaps the time has come for all involved to jetison dogma and to look at what there is to be done.

Unfortunately, like so much of the District's building boom, the new Georgetown was not so much planned as it was zoned. Rules governing the development of Georgetown south of M Street were established by the D.C. Zoning Commission in 1974, when it adopted a new, mixed-use waterfront category to replace existing commercial and industrial zones.

Challenged in court, the action was upheld in 1977. Developers moved in speedily to build on already assembled parcels of land. Although enlightened in some respects -- permitted densities were dramatically reduced in places and some residential use was encouraged -- the new rules stimulated buildings whose size spelled trouble for Georgetown's already crowded streets.

Georgetown Park, with 60-plus stores now open and 120 projected, is another nail in that coffin. M Street, a rush-hour hassle for drivers, pedestrians and residents alike, has become a sorry tangle on Saturdays and Sundays as well. Just about the best we can hope for on that northern border of the new city is a leveling off of traffic at some semitolerable level.

On the southern border, along K Street and the elevated Whitehurst Freeway, the District government has announced yet another study of the traffic problem. It is said to be focused upon the possibility of tearing down the freeway in favor of a broad, riverside boulevard. But who wants all those cars on K Street, even if it is given a fancy new name? Wouldn't this work at cross purpose to a desirable green riverside park? The time has come to consider the unspeakable: Fix up the freeway, learn to love it and get to work on the problem of brightening up dingy K Street under the freeway.

If traffic is the most immediate problem created by the new city, its biggest long-term headache may be finding people to live there. Costs forced developers to build mainly small units, expensive ones at that, and there are good indications that they overestimated demand. Or, to put it another way, how many rich singles and wealthy childless couples are there in the Washington area who are adventurous or crazy enough to want to live the new life style for more than a few months?

Still, the new Georgetown has a lot going for it. Individual buildings may stick out for their bigness and/or insipidity -- there is no striking solo masterpiece, but as an urban ensemble the new city projects a strong, positive architectural character.

Several existing buildings have been preserved and integrated with the new structures. Moreover, despite the number of architectural firms working there, a distinctive style has evolved, marked by a bit too much tastefulness but also by attention to the kinds of detail that make for visual interest: sculpted masses, variegated rooflines, richly inflected facades, strong entrance bays and so on.

The big architectural quibble is the near-universality of bricks. The Fine Arts Commission, which deserves credit for maintaining the general architectural excellence in the development, deserves the blame here. Relying upon historical precedent but paying too little attention to the size of so many of the new buildings, the commission bricked architects into submission time and again. Some variety -- stones, steel, glass, even paint -- would be welcome.

Ironically, the new city is a tremendous place to walk around. The pedestrian system of courtyards, paved pathways, covered walks and cascading stairs takes full advantage of the sloped terrain and the beauty of the C&O Canal, and presents an extraordinary succession of surprises. This series of spaces is a tribute to the skills of the individual architects who so engagingly fit their pieces into the overall puzzle. What an added delight it will be to walk there when -- if ever -- there's a park to get to down by the riverside.

If Georgetown Park is a big offender as a magnet for cars, it offers an irresistible enticement to pedestrians. The interior design is a playful, sophisticated, let-it-all-hang-out pastiche of the glass-and-steel Victorian shed. (The design is remarkable also for the number of voices that contributed, a team brought together by Herbert Miller, president of Western Development Corp., consisting of Alan Lockman Associates of Washington, Roger Sherman Associates of Detroit, Wah Yee Associates of Michigan and Clarke, Tribble, Harris and Li of Charlotte, Va.)

The place is a cornucopia of textures and styles, from the handsome tile patterns on the ground floor to skylights supported by pretty, ornamented steel columns and elbows. Hanging plants, yellow mums and potted trees look at home instead of lost on the way to a funeral. The storefronts themselves are a teasing melange of colors and pseudo-styles: Edwardian plush, California contemporary, Victorian purple, Art Nouveau elegance, you name it, a veritable blitz of sensations.

Nothing serves the experience quite so well as leaving it behind. Georgetown Park, by design and good fortune, serves that purpose admirably. Like so many of the new buildings, it connects in several places to the pleasant, irregular system of walkways that is becoming the distinguishing mark of the new Georgetown.

This is the outstanding strength, too, of Arthur Cotton Moore's scheme for Western Development's proposed Waterfront Development at the foot of Thomas Jefferson Place, the one okayed this week by the District's historic preservation agent. The centerpiece of Moore's design promises to be quite curious, visually, with a sort of stripped-down baroque colonnade (the column intervals punctuated by sleek turret-like cylinders) on two semicircular buildings that cradle a circular marina.

But if the design is eccentric, the planning is first-rate. It is interesting to note that the forms echo Edward Durrell Stone's original scheme for the Kennedy Center. Like Stone's first plan, but in much more practical ways, Moore's building opens itself up to the river, and genuinely promises to open the Georgetown waterfront to the public for the first time in decades. Access from 31st and 30th streets, as well as from Thomas Jefferson Place, is guaranteed; landscaping and an attractive esplanade are integral parts of the plan; the place will fit handsomely into any riverside park envisioned for the rest of the Georgetown waterfront.

So, in many ways, the waterfront development will be a splendid addition to the new city south of Georgetown, and it doesn't do badly by the rest of the city, either, old Georgetown included. It ought to be clear by now that the new Georgetown cannot be wished away.