A friend of mine makes a point of buying his cigarettes and sundries -- remember sundries? -- at the newsstand in the lobby of the Investment Building in midtown, and I must say the point is understandable. The building itself is one of those attractive Beaux-Arts commercial remnants that always offer a modest welcome, and the intimate lobby, with its fluted marble pilasters, monogrammed brass elevator doors and a faint, sweet smell coming from the hairdresser's salon, is sheer time-warp.

The idea is they don't build lobbies like that anymore, and it's true, for a long time they didn't. During the office building booms of the 1960s and 1970s, Washington developers and their architects seemed to vie with one another over who could build the tightest, most mean-spirited entrance and lobby spaces. This has changed in the last five years or so as we have entered the era of megaprojects and vast interior atriums, which, if they don't offer the friendly scale and understated flash of the old lobbies, do indeed open up these recent buildings in exciting new ways.

For this reason, in recent months I have watched work progress on the office building at 1615 L St. NW with special fascination. The entrance space and receiving areas of this midblock building seemed to promise something of the elegance and intimacy of the disappearing arcade-type lobbies along with the spatial pizazz of the new atriums. Now that the building is almost finished, I'm pleased to report that it delivers on this promise in spectacular fashion.

From a distance the building, designed by Robert Brannen of Jung/Brannen Associates of Boston in a joint venture with Vlastimil Koubek of Washington, doesn't appear to have all that much to offer. On the outside, rising above a two-story brick base facing L Street, is the sheerest glass curtain wall Washington has ever seen, a throwback, in stylistic terms, to the long nationwide run of International Style office buildings inaugurated by the 1952 Lever House in New York. Even the colors of the glass -- light-green vision panels separated by opaque, dark-green spandrel ribbons -- recall the 1950s. (The Lever House fac,ades themselves are composed in shades of green.)

As a general rule this kind of Modernism, with its flatness and strong horizontal striping, is the worst possible inspiration for designing fac,ades in downtown Washington -- mainly because our streets are too wide and our buildings too short to accommodate such emphatic horizontality -- and 1615 L does not escape some of the faults inherent in this treatment. The worst failing is that it simply stops at the top, like the quintessential D.C. speculative office box that, basically, it is.

Still, the building is something of an exception to this rule, for a number of reasons: The midblock site keeps it from being outlandishly prominent; the subtle greens of the glass catch the light, thereby softening the impression of bulk and bathing the street, at certain times of day, in a very interesting greenish luminescence; the fac,ades are varied a little bit here and there (for instance, with three tiny balcony notches on the top three floors at its southeastern corner, so placed to take advantage of the only good views of the city); and the curtain wall, made up of huge, state-of-the-art prefabricated panels, reflects a businesslike sense of conviction -- if you are going to do a box, do a box, and if you're going to do a curtain wall, do a curtain wall, the design seems to say.

Even so, the building wouldn't offer much to write about were it not for the interior spaces, at once spectacular and genuinely urbane. The first thing to say is that the interior brings back marble in a big way, and with it a tradition of ornament that had almost dried up with the triumph of the International Style. There are, in all, seven kinds of marble used, quarried in France, Spain and Italy and assembled and polished in Carrara, Italy, using a unique laminating-polishing process developed by Aldo Canali of Moliterno Stone, a Rhode Island company. The stones are beautiful in themselves, ranging in color from soft gray-beiges to luminous russets and pinks to speckled grays and deep blacks flecked with gold, and they were pieced together with extraordinary craft according to Brannen's geometric design.

The difficult corner fits are for the most part so precise that the whole procedure reminds one of the time nearly a century ago when Louis Sullivan was able to command: "No mutilation of pattern for the purpose of making a fit will be permitted." Of course, even given this exemplary handiwork the effect might be merely ostentatious. But it isn't. The effect is warm and pleasing, thanks in no small part to the crisp way Brannen's design of interwoven circles, diamonds, rectangles and stripes takes advantage of the colors and surfaces of the stones.

The progression of spaces is the second major strength of the interior. The entrance, two stories high and two bays wide, is tucked into the building's west corner, with clear-glass doors set back about 60 feet from the fac,ade. This two-story corridor, distinguished by the warm-toned walls and cylindrical columns partially wrapped in patterned marble, continues for another 50 feet or so before the space opens up into a six-story atrium.

Almost anywhere one looks in this atrium there is something of interest: a nook of a store (for a newsstand?) down a little flight of stairs, a second-floor office lobby not quite hidden away in the back of the building, a wall of glass on the west (glass block for the first two levels and clear glass the rest of the way up), a diagonal procession of terraces to the east, towering marble-sheathed elevator shafts, bridges on the fourth, fifth and sixth floors, and everywhere the play of natural and artificial light on the marble and glass surfaces.

Combining richness, elegance, spaciousness and intimacy, this ornamented atrium is altogether an interesting place to be -- an ironic turn of events in view of the building's sleek Modernist fac,ade, and a delightful surprise in view of the boxy, narrow exterior. In fact, the building is a whole lot bigger than it appears to be from L Street, thanks to a "brilliant land assembly," in the words of Joseph McMahon of the Beacon Companies of Boston, which developed the project in collaboration with the Washington and Metropolitan Life Insurance Co. "We started with just the parcel facing L Street," McMahon explains, "but by the time we finished we owned a much, much larger lot extending all the way to the alley in back of the National Geographic building."

Thus 1615 L St., all 400,000 leasable square feet of it, is more like two buildings than one: a narrow structure on L Street and a wider one on the alley. The lobby-atrium, which in effect joins the two buildings and provides views for office tenants who otherwise would have been trapped inside a giant L-shaped box, is a form of self-interest on the part of a developer aiming, again in McMahon's words, "at the very top of the speculative office market." This is the kind of enlightened self-interest that serves the public well, and the kind of aggressive competition from outside that has helped to shake up the smug Washington office development community.

Of course, whether the lobby-atrium lives up to its full potential as a lively urban interior space depends in large measure on the type of retail tenants the developer succeeds in attracting. (Please, Beacon Companies, no banks, no photo-processing stores and no cookie boutiques.) But thanks to the inventive way the architect carved out the interior space, and to his cheerful reintroduction there of the art of ornament, the chances are good. A few more buildings along these lines and we can celebrate in earnest the return of the lobby to Washington office buildings, sundries and all.