Alexandria has been given an architectural gift in the form of a new speculative office building on the King Street corridor -- a building that in most respects fits, and in some ways improves, its neighborhood despite its extra-large size. This improbable, impressive achievement, the work of Northern Virginia architects Zinser & Dunn Associates, represents a notable step ahead in a city that has had more than enough problems fitting new buildings into its distinctive historic context.

Brick with a bit of precast concrete trim, the building occupies three-quarters of a city block between King and Cameron streets on the south and north, respectively, and between Henry and Fayette streets on the east and west. It contains some 200,000 square feet of office and retail space and covered parking for more than 500 cars. It is seven stories high and rises, at its center, more than 90 feet.

It is, in other words, a massive thing -- just the wrong medicine for a historic district consisting mainly of interesting, older stores and houses no more than three stories high. But the architects, with the help of a willing client and advice from neighborhood groups and the city's planning office, ingeniously overcame many of the problems stemming from the building's dead-weight bulk.

And then they went an extra step by designing a building that projects a memorable image. The ironic result is a product that stands out from the existing neighborhood while being polite to it.

The first substantial gambit in this tricky game was to imitate the successful Washington strategy of stepping back the building mass in successive stages from three-story street frontage. As a consequence, from most points on the sidewalks surrounding the structure, its bulk and height are invisible.

But at certain key points, most notably the nicely detailed courtyard in front of the building's main entrance on North Henry Street, these qualities are celebrated. From there and from other, more distant, points, one sees that the building has a clock tower with a pyramidal top, framed by cylindrical masses topped with cone-shaped turrets.

The fact that these strong but ambivalent forms -- recalling French Renaissance, American Victorian and Art Deco precedents -- are not copies of motifs found in Alexandria's historic structures is perhaps one reason they fit comfortably: They are at once new and old, and are perfectly scaled. To stick "authentic" or ineptly adapted Federal-era cupolas and dormers atop 20th-century structures has for years been the favored Alexandria solution to the context problem. Zinser & Dunn's skillful, generalized, abstracted historicism is, demonstrably, a more promising tack.

The clock tower, which hides mechanical equipment for the elevators and ventilating systems, provides an emphatic vertical accent to a building that in all other respects is strongly horizontal. The careful detailing of the horizontal levels is yet another reason why the design succeeds.

For instance, there are attractive steel railings on the outer edges of each of the four setbacks and pointed precast concrete tops on the brick balusters on the upper level. Eyebrow canopies inserted at regular intervals along the seventh-floor copper roof give it a certain rhythmic distinction. Each of these touches, along with many others, helps to mediate the mass of the building, and to give it the enticing, whimsical kind of textures appropriate to its older, smaller neighbors.

The architects (with Barry Dunn as principal in charge) also took special care with the three-story street frontage of the building, as well they should have for a behemoth that stretches a total of 700 feet or so along four different streets. Short of designing each bay to look like a separate building -- clearly out of the question here for economic as well as esthetic reasons -- there is no way to disguise this kind of length.

Dunn, who grew up in a Victorian-era section of London, took a cue from his past by giving these Alexandria street fac,ades a stately rhythm: Light-colored second-story bay windows punctuate the fac,ades, as do inset vertical stripes of square glazed bricks whose soft rose hue complements the rich clay reds of the brick facing.

Other details give the big building the feel of a street lined with shops: The almost-square ground-floor windows, for instance, are framed with those elegant glazed bricks, and each is topped with a maroon canvas awning. Even the Fayette Street fac,ade, behind which are four levels of parking, has its distinguished rhythm: Here steel grill openings alternate with rectangular planes of glass block.

The interiors of the building also bear marks of a thoughtful, creative design. The floor plan inventively combines row-house-type offices fronting the streets with conventional open spaces on the top floors. Each is commodious in its way. Occupants of the row house offices will look out at the world through more interesting window shapes, while those in the upper floors can take advantage of broad, working balconies with spectacular views of the city. There also is, surprisingly, a very nicely designed skylit atrium in the middle of the building on the upper floors. Its basic function is to bring in some light, but Dunn made sure it was interesting to look at, too. He calls it his "tribute to Frank Lloyd Wright."

This building is by no means without flaws. The care in choice of materials and forms so evident elsewhere stops cold on the southern elevation set back from King Street, giving the structure an unfortunate sawed-off appearance from certain points of view. The windows are tinted blue-black, looking like ominous holes on the upper floors and like impenetrable screens at street level. And entrances to the restaurant and stores (most still to come) along King and Henry Streets are poorly placed and hard to find.

Still, flaws and all, this building is a spirited, sophisticated, significant addition to the Alexandria skyline and streetscape. The client, James Lewis of Tycon Developers, said he wanted a landmark structure, and he got what he wanted.