Architects for centuries have capitalized on the visibility and prominence of urban corners, sometimes with spectacular results. The Willard Hotel, for instance, is a great corner building.

But even modest intersections far away from grand avenues can stimulate architectural creativity. Eighteenth and T Streets NW, in the heart of a historic residential district near Dupont Circle, is one such lucky corner.

More than a century ago an architect celebrated the junction with a stylish turreted mansion on the northeast. Now, with this week's opening of the Lauriol Plaza Restaurant just across T Street, the humble intersection has two architectural marks of distinction.

Some of the freshest--and all of the most colorful and entertaining--architectural work in the Washington region of late and has been done in restaurants or clubs. In this sense, Lauriol Plaza is the continuation of a trend, yet another indication that, to a certain segment of the booming local restaurant industry, quality architecture is a critical part of the competitive equation.

But the new Lauriol Plaza is different from most of the other fine restaurant designs. It is not just an imaginative reconfiguration of an existing interior. It is the entire enchilada, a single-purpose building designed from the ground up by the young architectural firm of SiRu Architects, formed two years ago by Andrew Singletary and Guillermo Rueda.

The restaurant itself is not new. Longtime Washington restaurateur Raul Sanchez and chef Luis Reyes opened Lauriol Plaza 16 years ago in a reconditioned two-story building a block to the south, at 18th and S Streets NW. As the old building became more and more overstuffed, Sanchez and Reyes began to eye the underused lot at 18th and T Streets, occupied for years by a parking lot and a neighborhood liquor store.

"For Raul, this was like building his dream house," says architect Rueda. Initially, after the land purchase a couple years ago, the idea was to maximize the site's profit potential with a mixed-use, office-restaurant-retail building--the conventional approach. Gradually, however, it dawned on the restaurateurs that they ought to stick to doing what they do best and build a restaurant.

The decision, Sanchez recalls, allowed him for the first time to imagine how the restaurant of his dreams would function. The kitchen and its ancillary operations were his primary concerns. "What look the building would have, I really didn't care that much," he says.

For the architects, the idea of designing a restaurant from scratch was equally liberating. No longer required to squeeze in every possible square inch of leasable floor space, they were free to think about how best to shape spaces for the restaurant's different functions, and how these spaces might best be reflected on the building's exterior in a historic district with strong community oversight.

The result is a splendid little corner building, a modest tour de force of inside-outside dynamics. Unlike the turreted residence directly across T Street, the Lauriol Plaza building makes no obvious formal gesture in honor of its corner location. Rather, its primary facades are studied, rectangular compositions of solid and transparent planes. It is a polite, horizontal building with a sense of style.

But during business hours the building becomes both a generator and a container of energy. The towering windows of the main dining room, ranged in parade rhythm along 18th Street, enable diners to savor views of life on the sidewalks and streets outside, and passersby to enjoy reciprocal glimpses of relaxed patrons and scurrying waiters.

The sense of give and take is at once urban and urbane. And at nighttime, thanks in no small measure to the skillful work of Moran Coventry Lighting Associates, the scene becomes a magic one. Glowing softly from within, the busy restaurant with its tall windows and dramatically illuminated brick piers is an apparitional ocean liner, heading north toward Adams-Morgan.

Admittedly, in the full light of day the building still looks a bit naked in its slightly unfinished state. There is no sign above the door. The up-swooping canopy above the off-center entrance awaits its sheet-metal sheathing--at present, its exposed structural members look pained, resembling skeletal elephant tusks.

And the bright blue umbrellas outside don't quite make up for the fact that the sidewalk cafe does not yet exist--no tables, chairs, railing or wall-mounted canopy. These missing elements are important, because the attractive but rather flat 18th Street facade needs all the layering it can get.

The back of this building, incidentally, is every bit as appealing as the front although, appropriately, its character is more relaxed. In a nice gesture to nearby homes, the architects reduced the height of the rear portion of the building and gave it a graceful, curved roof covered in standing-seam metal sheets. The metal facing of the rear facade--a soft galvanized alloy--is a quietly inspired tribute to the visual informality of Washington's alleys.

Lauriol Plaza's spacious, varied interiors are a treat. You enter a low-ceilinged bar-and-waiting room and then, on a crowded evening . . . you wait. Fortunately, the spatial payoffs definitely are worth waiting for. Delivering on promises established by the crisp exteriors, the building's inside is a dynamic sequence of spaces that celebrates both movement and repose (with the scales tipped slightly in favor of the former).

First in line is a trip up a short flight of stairs to the main dining room, a long, high, loft-like space distinguished by those notable windows and Antonia Miguel's mural-sized painting of Seville. From this big room you ascend via cantilevered stairwell to a more intimate mezzanine dining area--the room with that distinctive curved ceiling, covered in Alvar Aalto-esque fashion with smooth strips of wood. From the mezzanine you climb--again via a nautical-industrial style stairwell--to the uncovered roof garden, where the wooden trellis supplies a frame for open sky. (The mezzanine and roof also are accessible by elevator.)

The detailing is a unity of opposites: Cold steel contrasts with warm woods throughout. Matter-of-fact fixtures such as clasps and brackets, attached with ordinary nuts and bolts, exude a certain poignant, look-at-me quality. To paraphrase Le Corbusier, Lauriol Plaza may be a machine for dining in, but it has a somewhat hand-made touch.

This commission was a break and a breakthrough for SiRu Architects. Singletary and Rueda met while working at the Washington firm of Keyes, Condon, Florance (now KCF/SHG), which has functioned over the years as a post-graduate school for many a Washington architect. The two clearly made good on their first major Washington job, blending modern architecture and conventional Washington politesse without breaking a sweat.

City corners are important. They are places of movement and fresh possibility. You get your bearings at the intersections of the urban grid. You turn the corner. You walk to the corner store. You hang out at the corner. You watch the world go by. In the Lauriol Plaza building SiRu Architects exploited these advantages to the full. As a result, the corner of 18th and T Streets today is more vividly alive than ever before.