I went for a walk in Rosslyn the other day, and I saw the tree.

To tell the truth, there are maybe a baker's dozen or so young trees doing battle there, but the idea of taking a stroll in that city of unlovely office buildings upon what once was a pleasant hill inspires the one- liner, if not outright derision.

No one can forget that something big went wrong in Rosslyn, almost everything, in fact, except for the smart money that capitalized on generous zoning and the boom in demand for offices near the capital. The interesting question now is, can anything go right in Rosslyn?

It is a question we can take seriously because, though very few people go to the trouble of walking in Rosslyn for the fun of it, quite a few do it out of necessity. Rosslyn is irrevocably there, and some 25,000 people go to work each day in those bulky towers. Thousands pass through, transferring from fast trains to restaurants or offices or slow buses. Hundreds stay in its hotels.

What caused me to take a stroll there was a talk I'd had with Thomas Parker and Diane Meier, planners with the Arlington County government, and another with David Pessanelli, a Washington designer whose firm submitted a thoughtful proposal for fixing up the Rosslyn walkways.

Parker, 43, a veteran of the Rosslyn wars, and Meier, 30, whose planning school idealism still runs strong, told a story of trees growing in Rosslyn, of parks and pleasant streets, of shops along raised arcades, of places to sit and rest and watch the world go by. They handed out a booklet that refers to those sorry-looking pedestrian bridges as the "Rosslyn Skywalk."

Meier did admit a rueful fact of Rosslyn life. "I guess," she said, "that all planners have to do the best with the site they're given." Parker said that "we want to correct the major deficiencies of the plan." Pessanelli, who has had some experience with remedial design, was succinct, "Rosslyn is a challenge." (His company was able to fix up the entrances to the sleek uptown Mazza Galerie so that the place does not look as if it were closed 24 hours a day.)

Parker and Meier did have some fairly impressive facts to back up their vision. In the next three years or so, four parks will enliven the Rosslyn scene.

One is already in place. It is a pleasant if hard-surfaced little park designed by the local firm of Donovan, Feola, Balderson & Associates for the plot across North Moore Street from the Metro station. Another, slightly larger and greener "vest pocket" park on the same block is currently under design by the SWA Group of Boston, with Peter Walker, chairman of landscape architecture at Harvard, in charge. Parker pointed out proudly that both of these parks are financed by developers as part of Rosslyn's incentive zoning system.

The most innovative of the new parks will be the one at Rosslyn's south end, where a cluster of buildings confronts a gaggle of highways. Commissioned by the county, this park is being designed in toto by an environmental artist, Nancy Holt.

At Rosslyn's other end, where it confronts Key Bridge, the Williamsburg firm of Abbott Associates has designed a huge park. It will bridge Fort Myer Drive on a platform atop Interstate 66, the burrowed superhighway, and will be connected by a pedestrian bridge to the Rosslyn walkway system and to the Marriott Hotel parking lot. (This is the site that, not so long ago, the county government thought would be nice for a heliport.)

To complement these new parks, the planners have two major projects on the books, though the books are mostly on the shelf due to lack of money. The first concerns the Rosslyn "Skywalk," which has potential even if the name raises hyperbolic expectations. Even calling the Rosslyn pedestrian bridges a "system of walkways" is at present a gross exaggeration, although as Pessanelli points out it need not be so.

With any luck at all his firm will soon begin work on the first, $100,000-phase of a program to make the walkways comprehensible and alluring with signs, maps and other minor design changes. Citizens, developers and county officials should be aware, however, that it will take more than this to fully exploit the potential of the walkways. Because they were left to the design whims of private developers (as part of the incentive trade-off), the walkways are ugly and confusing. To make them passably attractive without gimmicks will be, as Pessanelli says, a challenge.

The second, related, project has to do with Rosslyn under the bridges -- at street level, which motorist and pedestrian alike know to be both brutish and boring. The idea is simple, apt and, under the circumstances, almost breathtaking: widen the sidewalks and line those streets on both sides with trees . . . a beautiful idea that would make the streets easy to cross, the sidewalks pleasant to walk upon, the shops more attractive and numerous, and even, to an important degree, soften Rosslyn's hard and ugly impact.

Here too, money problems are in the way. The county government approved a $500,000 project for three key Rosslyn blocks to demonstrate the beauty of the idea for the developers, who would be asked to pay for its completion, but federal cutbacks in other areas have scotched that scheme. Basically, this imaginative plan is now in the hands of Rosslyn's owners and developers, some for it, some against.

Perhaps it will never get done. There are those who would say that Rosslyn is beyond repair. It is true that Rosslyn will never be beautiful, but it need not be as nasty as it is today. The day may even come when walking there would a treat.

The real lesson in this little tale, however, is that if early on the Arlington planners had paid more than lip service to excellence they would not have had to engage in catch-up, fix-up efforts. Those trees in Rosslyn might be 15 years old today, and we could all rest easier about Court House Square, Clarendon and Ballston -- the next dominoes in the Arlington development line.