If this city ever has a renaissance - and heaven knows it needs one - it will happen despite its flashy Renaissance Center.

The year-old, skyscraping bundle of glass tubes on the Detroit River is really a Counter-Renaissance Center. It consists of 73-story, 1,400 room hotel: meeting rooms and halls for large conventions, four office towers with 2.2 million square feet of rentable space, parking for 6,000 cars, and a carnival of four movie theaters, 13 restaurants, a suburban-shopping-center-worth of shops, cocktail lounges, splashing water, greenery, glitter and Muzak-drenched confusion.

All this obviously draws business, people and vitality from Detroit's already decaying downtown six or seven blocks away. Once you have entered the RenCen, as Detroiters call it, there is no reason to step out again until it is time to go home or your money runs out.

But entering RenCen is extremely difficult if you attempt it on foot. My excuse for being so maladroit in Detroit is that, before my visit, i had dinner nearby and there weren't any taxis. So, with much apprehension (Detroit has one of the country's highest crime rates), I negotiated several deserted and partly abondoned blocks of urban no-man's land until I came to a formidable barrier - 10 lane Jefferson Avenue, a nasty highway that clearly was not designed to be crossed by anything.

You must pass two more tests before you may be admitted to architect John Portman's never-never mega-structure.

First, you muJohn Portman's never-never mega-structure.

First, you must prove your courage by walking the driveway through a forbidding "berm," a concrete rampart that looks suspiciously like a Berlin Wall there to keep the natives out, but was built, I am told, to house heating and air-conditioning machinery.

Next you must prove your ingenuity by finding your way through a labyrinth of driveways without signs or sidewalks, until you find the all but hidden entrance into drive-in Portman-land.

The reward is that once inside you may plunk into any one of a myriad of cushiony seats on any of six levels - by the pond, under a waterfall, perching on a daringly ca tilevered "cocktail pod" - looking up into dangling greenery or down on teeming humanity - and , at the flash of your credit card, an apprition will appear on a motorized refreshment wagon and sell you a drink.TThe scene is at once lively and monotonous. You are inside the huge platform from which all the glass tubes sprout. It is an enormous, exciting space, filled with the giant concrete columns that support the skycrapers above, as well as elevator shafts, a multitude of escalators, spiral staircases that mesh various levels and gallerie and pods and ends that made Portman famous with his more restrained Peachtree Center in Atlanta and Embarcadero Center in San Francisco.

The scene is monotonous once you walk around. In Detroit, the combined hotel lobby and shopping mall form a circle. You walk around and around expecting some surprise, but it is always the same. You get dizzy and confused. I never quite knew where I was. The poor graphics did not help.

What would help, in addition to signs, are different shops and window displays. Although the office space is renting well, few RenCen shops have opened. You see only what seems like miles of boarded up space. And you also seem to see every cubic inch of the 25,000 cubic yards of concrete that has been poured into this structure.

RenCen is touted as one of the largest privately financed urban development projects in the nation's history. It was launched on the initiative of Henry Ford II for the often expressed purpose of helping Detroit out of its despair, of showing confidence in the city. By the time it was finished, it showed over half a billion dollars worth of confidence. Ford was joined by 50 other corporations.

Wayne Doran, the amiable and frank spokesman for the RenCen investors, says the demonstration of confidence is as much psychological as physical. Psychologicaly, it may indeed have accelerated talk about new skycrapers and shopping centers in downtown Detroit. There is also the promist of a federal demonstration grant for a 2 1/2 mile "people mover" system that would link the central business district with the cultural center - the Art Institute (one of the best museums in the country), the library and Wayne State University - further up Woodward Avenue. Psychologically, it is also true, no doubt, that the sight of the gleaming glass tubes make many a Detroit heart beat faster - although you see it far more prominently from the Canadian side of the river.

But while Mayor Coleman Young is loudly and frequently praising RenCen, I heard much bitter talk on the part of Detroit housing and planning officials about it. Some see it as a capitalist plot against the city.

The bitterness is understandable if you travel around the city. It is indeed "the city of urban despair," as one writer called it. Block after block of abandoned, looted and burned detached cottages on weedy, littered plots look even worse than the abandoned, looted and burned-out tenements in Brooklyn. The shocking sight is one occupied house, in a sea of dead ones, with a Horde of children playing in the debris of a broken-down porch.

RenCen does nothing for these children and Doran says irrefutably that it never promised to solve the city's social problems. It provides 3,000 jobs, and is bringing thousands of conventioneers into the city. The troubel is, few of them venture across Jefferson Avenue.

The city, together with RenCen, will have to spend thought and money on building links to downtown, if the investment is to stop hurting Detroit and start helping it. Well-lit greenways and walkways and minibus service to the restaurants and boutiques of Greektown and other attractions are imperative. The sooner that silly "berm" is buried the better.

I am sure the deplorable insularity of RenCen is not due to ill will, as some people charge, but to the naivete of American business in matters of city planning and architecture. The river-front site was easily available (although city planners wanted it to be a park). There was no need, as Doran pointed out, to displace anyone. And it had a good view.

What is more, Ford and his partners are not the only developers who got high on giddy height. The Promethean power of scraping the sky is seductive. The affliction is not confined to Manhattan and Chicago. Often to their subsequent regret, developers as far away as Paris have succumbed to it.

Just think what downtown detroit would be like today if Ford had built his soaring glass tubes on end. RenCen would have yielded at least 12 square blocks of new buildings - greenery, splashing water, glitter, Muzak-drenched confusion and motorized bar maids and all.