The paradox of one of the best-looking new office buildings in the city is that it cannot really be seen until one is hard upon it in narrow Georgetown streets heading down toward the waterfront.

However, once it has been discovered it leaves a definite, lasting impression. The building, Jefferson Court, situated at the foot of the Georgetown hill between Thomas Jefferson and 30th streets NW, projects the kind of sturdy resplendence normally associated with structures from an older, sturdier time.

How much better it is than the typical Washington box may be gauged simply by comparing it with a couple of contemporaneous structures across Thomas Jefferson Street -- buildings with all the charm of brick dumplings.

According to Richard Giegengack of the Washington office of Skidmore, Owings and Merrill, the primary historical sources for Jefferson Court were the muscular buildings of H.H. Richardson, the great 19th-century American architect, and, for the alluring masonry courtyards, certain facets of Moorish buildings such as the Court of Lions in the Alhambra in Granada, Spain.

The Richardson influence is directly visible in the building's magnificent entrance arches on both Thomas Jefferson and 30th streets. Though Richardson's arches were usually of rough stone and these are of brick, they sing with the same kind of authority as his did. With nine curving courses of brick above the spring line (where the arch meets the carrying column), they are, to paraphrase the late Louis Kahn, just what arches want to be -- they expand with great force, they convincingly carry weight, and, not incidentally, they make one want to pass underneath.

(Richardson could, and did, make the occasional splendid brick arch. In the 1880s he made two of them, in fact, for the adjoining houses of John Hay and Henry Adams at 16th and H streets NW, where the aptly named Hay-Adams Hotel now stands. The master's more customary approach is reflected in the entrance arches of W. Edbrooke's Richardsonian Old Post Office building on Pennsylvania Avenue.)

But the Richardsonian inspiration at Jefferson Court is apparent in more than just the details, even details so paramount as these arches. It's more a question of spirit. Although the building does not actually look like one that Richardson would have designed, it possesses the vivid, robust quality that Richardson so often gave his buildings.

The sides are enlivened with bays that manage to be both weighty and graceful. The windows are appropriately varied. The ground floors, east and west, are distinguished by sequences of arches that grow from the main spans. And the rooftops, even from the squeezed perspective forced by the setting, present vigorous, picturesque silhouettes with their pewter-colored metal-roofed turrets, pediments, sloping glass and metal surfaces, and paired cylindrical brick chimneys (left over, and happily so, from the time the building was conceived with residences on the top two floors).

The open courtyards of Jefferson Court are extraordinarily pleasant, and promise to become more so as climbing vines grow and begin to cling to attractive metalwork arbors attached to the walls. The derivation from the Alhambra is distant -- it's mainly a matter of water, which the architects have allowed to flow pleasingly in a narrow trough, following the slope of the land from one central fountain to another.

If the water counts for a lot, the plan of the adjoining courtyards counts for more. Jefferson Court is, in reality, two rather large office structures, each with its separate (and handsome) lobby, tied together in the interior courts. "We started out with the idea of a big, single courtyard but it didn't work as well," Giegengack says. The architects ended up with the present configuration of rectangular spaces connected on a diagonal line.

One of the advantages of this arrangement is that people will use it as a shortcut -- the active diagonal line is almost always better for this purpose than a right-angled shape in the city grid. Once in the courts, pedestrians will be tempted to tarry not so much by the ground-floor shops, which are primarily there to serve the captive office audience, as by the enchanting nature of the spaces themselves, with their sequences of enticing views.

All of this is quite a feat for what is, in many respects, a conventional speculative office venture. Part of the credit is due the developer, the giant Texas-based Trammell Crow Co., which wanted a premier product for its Washington debut and hence was willing to go the extra mile for design and materials. One hopes the company does not leave it at that, for there is many a vacant lot in downtown that would profit from similar attention.

Still, it is the architects -- SOM partners Giegengack and David Childs and senior designer Milo Meacham -- who deserve our most abundant applause. Measures of their public-spirited approach are the thoughtful urban design touches that are built into the plan -- not only the diagonal walk-through that adds significantly to the sequence of walkable spaces in lower Georgetown, but also such things as the covered arcade along Thomas Jefferson Street that connects to the existing arcade of the Foundry building, and the commodious setbacks from K Street, which other recent builders have treated as if it were an alley and not a city street.

The fact that this is a foreground building in a distinctly background setting is due partially to the obstruction of the Whitehurst Freeway. "When we designed this building we were hoping it would come down," Giegengack says. The unfortunate result is that, unlike Arthur Cotton Moore's Washington Harbour, the picturesque fantasy land with waterfront exposure now rising just across K Street, Jefferson Court is well nigh invisible until one is almost inside its doors.

Even so, this is one of the nicest new buildings in town, a massive structure combining boldness and strength with a certain delicacy in detail.