THE HUGE Far East Trade Center building proposed for Washington's Chinatown, with its pagoda-style sunscreens attached to a dark mirror-glass facade, may be the biggest chunk of Chinese-American pastry cake you'll ever see. But you have to admire the ethnic pride and overall chutzpah of the thing.

The building is intended, its architects say, as "the anchor for a new Chinatown," and when the builders break ground early next February to help ring in the Chinese new year, I think we can safely begin to bid a fond farewell to the faded charm of the old Chinatown.

Between now and then the District government has a chance, probably its last, to preserve something of the texture of the place simply by ratifying the downtown historic district proposed last summer by the Joint Committee on Landmarks. The choice takes on an added urgency now that we have something concrete to contemplate, concerning the physical form and economic mix of the Chinatown of the future.

And boy, is it something, this Far East Trade Center building. Located on the southeast corner of the key Chinatown intersection, 7th and H streets NW, it stretches the full length of the 7th Street block south to G Street--nearly 450 feet from edge to edge. Its main masses will be 110 feet high, with a "lounge-cum-dance-hall" rising to 130 feet just off-center along the 7th Street facade.

Thus described, it is the cake without its all-important icing--an elongated version of the typical Washington box, its form largely determined by high-density commercial zoning and the city's height restrictions.

True, the sheer size of the building is unfortunate, and so is the monolithic massing, relieved only by an angled cut in the 7th Street facade. A more restrained solution, sympathetic to the three- and four-story buildings on the other side of 7th Street, would have been to push the principal mass of the structure back by building lower along the streets.

But restraint was hardly the watchword for Alfred H. Liu, the building's principal designer. Liu clearly wanted to make an emphatic, full-speed-ahead statement, and he did it in no uncertain terms. "Alfred's concept, really his dream," said one of his colleagues in the firm of AEPA/Architects, "is to create a new image of America's Chinatowns." The building he designed will be a polychrome decorated box unlike any we've seen before, a stretched-out high-tech cube with an ethnic post-modern veneer.

The basic skin of the building will be a dark mirror-glass curtain wall. Attached to this in an irregular pattern of horizontal stripes will be those pagoda-style sunscreens topped with yellow, orange or golden tiles and attached to rounded, red-painted pilasters. Ground-floor shops, set back 20 feet, will be protected by an arcade supported by red columns. The main entrance, along 7th Street, will be emphasized by a tiled Chinese gateway rising more than 40 feet. Towering behind this in a recessed niche will be the pagoda-roofed dance-hall bar, served by exposed "Chinese lantern" elevators.

My, oh my. What we're getting, Liu has said, is a "pagoda floating in the clouds." Another take is that we're getting a really oddball blow-up of Chinese-American restaurant decor into the world of mega-buildings.

This change of scale is wild--it is like multiplying by 100 times the four-story On Leong Merchants Association building on H Street--but the design has the merit of uncompromising brassiness tempered, at least in theory, by a certain elegance. Liu has the courage of his convictions. He doesn't try to hide the size. Indeed, the sleek horizontal sweep of those projecting sunscreens will focus our attention on the building's size and shape.

And whether you hate it or love it, you won't be able to pretend it doesn't exist. This unforgettability factor is no small thing in a downtown being rebuilt, in the main, with more or less indistinguishable boxes: The building will function as a huge sign telling us we've arrived in the new Chinatown. If only it were not, itself, so damnably big and boxy.

It is hard to believe so much is needed. Can Chinatown, even the brave new Chinatown of Liu's dream, really support 200,000 square feet of added retail space?

Still, the proposed mixture of uses--a 527-room hotel connected to an office structure and retail, exhibition and performance areas with an oriental flavor--makes very good sense. And in certain basic respects the building design is ingenious and crisply intelligent. There is more to the building than its Chinese-modern skin.

In the ground-floor plan, for instance, every effort has been made to open the building to pedestrian life. Stores face the streets on three sides (the fourth side is an alley) and there are spacious entryways in three places--at the corners and on G Street--in addition to the dramatic, angled atrium entrance on 7th Street. On the inside the space flows handsomely toward the atrium, which neatly ties the various elements (hotel, office and retail) together. Direct underground access to and from existing Metro stations--the Connecticut Connection idea repeated twice--will contribute to the liveliness of the place.

The final result will depend a lot upon the success of the center's management in attracting Far Eastern businesses and arranging a healthy mix of stores and restaurants. The ultimate look of the building depends a lot upon the refinement of key design details such as selecting materials and the precise colors and sizes of the parts. If the developers decide to go cheap on materials we'll get an embarrassing ugly duckling. If not, the result may be an overlarge but somehow lovable lemon.

The key issue of how the building fits with the old Chinatown already has been decided. It doesn't really fit. And certainly one behemoth signpost is enough.

This is why it is important that the Barry administration embrace the historic district downtown, a significant segment of which is in Chinatown. In their low scale and their variety of materials and styles, the remaining clusters provide breathing spaces between the mega-blocks. If we let the old buildings go, as they surely will without protection, we can never get them back.