The street in front of it is blocked with chain link fence, its stores are empty, there are as yet no office tenants to enjoy its privileged views and a few of the recently planted locust trees in its entrance plaza have died, but the new office building at 3100 Clarendon Blvd. in Arlington already has delivered much of what was promised -- it truly is a landmark tower for the Clarendon of the future, quite the best of the big new office buildings in burgeoning Northern Virginia.

The ominousness of the building's emptiness is misleading. This temporary phenomenon, caused by the tremendous amount of office construction elsewhere along and beyond Metrorail's Orange Line, can even be viewed as a golden opportunity, a pause during which residents, planners, politicians, developers, prospective office tenants, merchants, etc., can yet again ponder the still unanswered question: What should be the Clarendon of the future?

Clarendon of the past -- commercial Clarendon, that is, centered mainly on Wilson Boulevard but spilling onto Washington and Clarendon boulevards (formerly Fairfax Drive) -- was a lively strip of modest art deco and streamlined stores serving neighborhood and regional needs. Remarkably, even though a patch of it was demolished for the Metro station, its ghost survives almost intact behind altered or abandoned storefronts.

Clarendon of the present, a victim of fierce competition from regional malls, is not wholly an uninteresting mix. There's the run of muffler, carpet and furniture outlets usual to decimated strips, but also the Washington area's most cohesive gathering of Vietnamese and other Asian stores and restaurants as well as a few isolated enterprises of similar distinction. (The new Ferrari parked proudly in front of the aptly named Thorobred Motorcars could be mistaken for Arlington County's sleekest public artwork.)

Clarendon of the future, as currently planned, is not a happy prospect. What could happen, should all the commercial properties be developed according to currently permissible "matter of right" zoning, is chillingly demonstrated by Clarendon Square, a new seven-story office building that takes up a full block of Wilson Boulevard between North Highland and North Garfield streets. This run-of-the-mill modern building is perverse in its willful disregard of everything -- scale, street patterns, architectural shapes and styles -- that once made Clarendon distinctive.

To make matters worse, the Clarendon Sector Plan, a compromise painstakingly worked out a few years back, contains an incentive zoning category that could speed the obliteration of the old Clarendon. Heights, according to this regulation, will decline progressively as the new buildings approach nearby residential neighborhoods, but despite encouraging words about preservation, the biggest buildings are permitted to front directly on the boulevards on sites currently occupied by lower, older structures. Obviously it's a compromise that developers with clear-and-build mentalities can live with.

Which brings us back to the new tower, a sizable building of sizable appeal. Designed by Martin & Jones of Washington (with Vlastimil Koubek doing the detailed, "working" drawings), it has that early '80s postmodernist look. Both Guy Martin and David Jones encountered Michael Graves while they were students at Princeton; while designing the building (in the early '80s, of course) they sometimes called it "Portland East" in jocular homage to Graves' Municipal Building in Portland, Ore., which was on everybody's mind at the time. Their product does roughly resemble his, and it also is a bit too blunt. But what it lacks in delicacy it makes up in clout; it presents a memorable image and it has lots of lessons to teach.

It's a natural crossroads building on a prominent crossroads site. Those who, like the National Capital Planning Commission (and, among others, myself), opposed its construction on the justifiable grounds that it would permanently disrupt the vista from the U.S. Capitol into the gentle green hills of the west are bound to resent it some. When seen from the west steps of the Capitol it does as predicted: With its pyramidal cap it pierces irrevocably the tree line of the hills.

But the time has come to be graceful losers -- the juggernaut of development along the Orange Line in Virginia continues unabated, and none of the midrise buildings along the route are nearly as distinguished as this one. Its top is not so objectionable as I had anticipated -- unlike Philip Johnson's proposed PortAmerica skyscraper in Prince George's County, this 14-story building is so compressed that no one will mistake it for a symbolic equivalent of the Washington Monument. The mimicry here, perhaps unintended, is almost affectionate.

From the other direction, from the three broad streets (Washington and Wilson boulevards and Fairfax Drive) that come together from the west in Clarendon, it's a sensational magnet. The stepped-back massing of the building, culminating in the pyramidal top, clearly was intended to recall that of many distinctive public buildings of the 1920s and 1930s. The transitions from part to part of this building are not nearly so fine as those of the masterpieces of that era -- it reads almost like a giant three-dimensional, tricolor poster, but as such it's a tour de force. The pyramidal top and those giant square windows centered among countless smaller squares are irresistible beacons.

From medium range, say, a block away, one begins to recognize further niceties of the design -- the way the tower is twistingly sited in the middle of a big triangular block, the way its height and bulk recede in favor of two-story retail and office fac ades at street level, the way certain other architectural motifs of nearby stores are picked up. The three cylindrical corners of the building are together an inspired example of contextualism -- earlier architects, picking up on the pattern of oddly angled intersections, made the cylindrical corner Clarendon's paramount architectural form, and here it is restated with authority.

This building gives one lots of reasons to like it up close, too. The materials -- granite panels of differing colors and degrees of polish -- are appealing, the storefronts are nicely (and plainly) designed, entryways are properly declamatory, through connections for pedestrians (including an as-yet unopened underground link to Metro) are well placed, and the public spaces are inviting.

The entrance plaza, in telling contradistinction to the do-nothing open space in front of Clarendon Square, is a genuine place, its walls gently welcoming like cupped hands. And one can imagine the new strip park facing Wilson Boulevard (designed by Martin & Jones with landscape architect Cales Givens) as a great place to gather -- it's like the center island on Broadway in Manhattan's Upper West Side, a good model for a lively urban place.

Therein is the Clarendon rub, of course. It's neither lively nor urban, and there's no sure blueprint to make it so. The fortuitous pause in development cannot last for too long, but there is some time in which to reexamine the ground rules as they now stand. Fortunately the Arlington County Board has designated a task force to do just that, with particular emphasis on historic preservation and open-space needs.

This task force has its work cut out for it -- incentives for healthy residential and retail development are pathetically weak -- but preservation consciousness is crucial. The architects of this strikingly sympathetic new building pointed in the right design direction, but behind those decaying fac ades lie the real keys to the image and the reality of Clarendon's future.