The view from the window of Henry Glassie's eighth-floor law office in the Sun Building, Washington's first skyscraper, tells a tale of two cities.

Inside it is circa 1887: soft mauve-colored walls, oak moldings, cast-iron fireplace, Victorian-era paintings. Outside, directly across the street, 1983 makes itself emphatically felt in the long brick, glass and concrete grid of the huge Quadrangle-Marriott building.

Pure preservationists would call it a Jekyll-and-Hyde tale, the recently restored Sun Building on the north side of the 1300 block of F Street NW playing Jekyll to Quadrangle-Marriott's Hyde on the south side. But the larger story is subtler, more complex and more promising.

Truth to tell, there are more than two architectural styles and building types and uses that must learn to coexist if the old downtown is to become the born-again center of work, commerce and entertainment we hear so much about. Given some skill and foresight on the part of planners, owners, developers, architects and merchants--and not without some luck--this block could help lead the way.

The restoration of the Sun Building, 1317 F St. NW, makes a good beginning. Another new spark on the block, which used to be part of the liveliest retail strip in the Washington area, is the ingenious rejuvenation of the Adams Building at 1333 F St. NW.

The two office projects are wildly different in many ways--the one, an attempt to recapture the spirit of a 19th-century original; the other, an effort to recycle a sleek 1940s add-on that in itself was a desecration of a 19th-century structure--but that is just the point. Together they suggest rich possibilities for their own and surrounding blocks. New meeting old is by necessity the main theme of downtown revitalization.

The Sun Building was commissioned in the mid-1880s to become Washington headquarters for the Baltimore Sun (which later sold the property to a bank). It was designed by Alfred B. Mullett, whose earlier contributions to the Washington scene include that remarkable Second Empire pile, the State, War and Navy building (now the Old Executive Office building) west of the White House.

Like the rest of the old downtown, the property had gone downhill, its high-ceilinged offices mostly empty, its face of rusticated marble dirty and crumbling, its ground floor ruined by incongruous store-front additions, its 35-foot-high clock steeple unceremoniously lopped off. Today, thanks to the entrepreneurial foresight of its owner-occupants--the law firm of Glassie, Pewett, Dudley, Beebe & Shanks--and to the skills of its architects (Abel & Weinstein) and contractors (Gordon & Maizel Construction Co.), the Sun Building shines again both inside and out.

Working from photographs and Mullett's plans, and aided by architectural historian Dudley Brown and architect Emily Eig of Traceries, this team was able to bring back the perky modulation and textural richness of Mullett's facade, from its two-story arched entranceway at ground level through its five-story bays to its lively gabled roofline.

Nor does the treat stop there. Something of the former flavor of the narrow, high-ceilinged lobby has been recaptured by craft and guesswork, and offices, stairwells and hallways have been sympathetically restored to much of their previous glory.

One can quibble with details here and there, with air-conditioning ducts that look forlornly out of place near stucco moldings, with rusticated "stonework" that matches the strange, yellowish color of the original marble but is jarringly slapdash in texture. Basically, though, the restoration is first-rate, an unusual case that, with the help of new federal tax incentives favoring preservation over demolition, can profitably be repeated elsewhere in the old downtown.

The story of the Adams Building, so-called because the site once accommodated the Washington residence of John Quincy Adams, has an ironic twist. The seven-story building was completed in 1886, a year before Mullett's higher structure down the block. But in 1948 the ornamental cast-iron front of the Adams Building was stripped and replaced with a patterned facade of polished granite.

This was just two years before the Sun Building owners demolished Mullett's striking steeple (which, unfortunately, was not part of the recent restoration). Newness reigned in the '40s and '50s, a time when countless main streets across the country were disfigured by paste-on facades. Obviously, F Street was no exception. The mania continues even today, with new paste-ons replacing old ones. (Not long ago, for instance, a shoe store added yet another inept ground-floor window treatment to an exquisite little Art Deco building at 1309 F St. NW)

The 1948 face given the Adams Building was more ambitious than most--it covered the whole building, top-to-bottom, with three-inch thick slabs of carnelian granite. This fac,ade was a classic of its kind, a '40s commercial composition very close to its asymmetrical best. Working with what was there, architects Thomas Georgelas & Associates cannily manage to preserve the panache of this "original" by removing 30-inch-high granite courses and replacing them with ribbon windows.

Even better, they created a new ground floor that makes sense, adroitly fitting both retail and office entrances to the color, scale and style of the existing facade. Stylistically a world apart from the nearby Sun Building, the new Adams facade shares with its neighbor this sense of architectural wholeness and urbane amenity. Every other building on the north side of the block, including such notable historic structures as the Westerley Building at 14th and F streets, would greatly benefit from such care.

This is but one of the lessons to be learned from these new F Street projects (and, it should be noted, from the new Quadrangle-Marriott building on the south side of the street, with its retail canopy stretching more than halfway along the block). Another is the relatively small scale of the projects: If much of the rest of downtown could be redeveloped on a piecemeal basis, instead of in the large chunks preferred by most developers, all of us would benefit. Still another is the shrewd use of federal tax credits that helped to save the Sun Building.

Besides, the "new" Sun and Adams buildings were done with spirit and intelligence.