Washington is becoming known as a city of architectural innovation. This is a new role. Assessors of taste and style typically have viewed the city as a conservative follower rather than inventive leader, as a city picking up on design trends, not setting them.

In the last few years, however, Washington has been instrumental in giving birth to facadism, whose several manifestations all result from common motives: a nostalgic and intellectual desire to preserve or recreate architecture of the past, dissatisfaction with many of the buildings and stylistic attributes of orthodox modernism and current income tax regulations favoring investment in historic structures.

Architects choosing to recall the past in new buildings can make new facades that look like old ones, either literally or figuratively. They may incorporate salvaged antique components or newly fabricated elements -- classical columns, capitals, arches, pediments, cornices, moldings. Sometimes, whole facades considered historically significant are saved and embodied in new construction.

Skidmore, Owings & Merrill demonstrated "new-as-old" facadism (and the firm's stylistic flexibility) by designing the mammoth Doan Building facing New York Avenue and H Street NW. Shortly thereafter, its turreted and arched brick office building abutting the Whitehurst Freeway rose in Georgetown. The former makes vague reference to a pilastered palazzo with its abstracted, neoclassical facade and figurative decoration, while the latter serves up images both Victorian and Roman in flavor.

Another exmaple of new-as-old facadism is 1718 Connecticut Ave., an office building of collaged elements designed from scratch by David Schwarz's firm. It, too, makes references to past architecture with arched entrances, varietal windows, towers, neo-Romanesque details and coloration.

The building attempts to fit comfortably within the existing facade context along the west side of the avenue and, if you aren't looking for it, you might not notice it. But if you do look thoroughly, you discover that the building sheds its frontal red brick and stone garb on the alley side for less costly, white, international-style clothing. Is there a message here?

At K and 25th NW is an apartment building, designed by Martin and Jones, whose general massing and color (beige and red brick) blend well with the surrounding buildings. But if you look further, you also notice just-constructed classical fragments applied here and there to an otherwise systematic, modern facade. These fragments allude to rusticated stone bases, pieces of arcades or entablatures, as if the new building had been built inside some partial archeological ruin, or its memory.

Likewise, their red brick bank building at the corner of M and 29th in Georgetown is a new edifice decorated with a seemingly random assortment of referential classical fragments -- occasional Doric columns, partial entablatures, cornices, Palladian windows -- at once reminiscent of Federal, Victorian and Beaux Arts motifs.

Not far away, across the Whitehurst and fronting on the Potomac River, is Arthur Cotton Moore's mixed-use Washington Harbor project, now under construction. Enough is in place to reveal that this, too, employs fabricated antiquity, cast in concrete or veneered in several shades of brick, to recall the many and diverse elements of Greek, Roman and Renaissance architecture in one eclectic and complex collage.

Completing the new-as-old cycle is pure revivalism, symbolized by Hartmen-Cox's new neoclassical Market Square project planned for 8th and Pennsylvania NW. These buildings, a pair of quarter-crescents, will appear as direct adaptations of the cornice line new-classicism of the Federal Triangle across the avenue.

"New-plus-old" facadism, likewise one of D.C.'s latest trends, results in some projects that escape notice while others are inescapable. Among the most notable is Red Lion Row at 2000 Pennsylvania Ave. NW. Designed by John Carl Warnecke and Helmuth, Obata & Kassabaum, this project epitomizes the difficulties and opportunities faced by architects and developers when building new structures next to, behind or over old ones.

Red Lion Row is characterized by the stark contrast between the block-long, late-19th-century row house facades at the street edge and the new, modern, flush-skin, concrete and glass, ribbon-windowed office building behind them. While the designers wanted to make the new building recessive and invisible, a "background" building, this may have been almost impossible to achieve adjacent to so wide an avenue.

Compare it to the more-subtly-integrated office building and row house project at N and 19th NW. Here, David Schwarz styled the new building, rising several stories above and behind the brick-faced row houses, to reduce the potential visual contrast. The new office volume is faced in red brick, its windows are "punched" rather than ribboned in the wall surface, and its brick detailing imparts greater domestic character to the structure than a conventional curtain wall might provide.

Even more subtle, but more clearly replicative, is the addition atop 1915 Eye St. NW, which is not easy to spot. Four stories were added by stepping back successive floors and, at the face of each receding level, repeating the pediment-like profile capping the building's original facade. The addition was designed by the Kerns Group.

In a league by itself is a project on the northwest corner of 18th and F NW. At first glace, it appears to be a clone of Red Lion Row -- a modern office building behind and above a small group of Victorian row houses. However, closer scrutiny reveals that the row houses are not old, but are a new segment of the office building with an equally new, applied Victorian skin. Lacking something antique to save, the architect and developer nevertheless must have felt compelled to create that impression . . . or illusion.

Keyes, Condon and Florance's Design Center at D and 4th SW started with a huge, old, windowless, storage building. The architects chose a new-plus-old strategy involving preservation and new construction. Yet they resisted importing historicist elements not there implicitly.

The new addition on the east side is rendered in its own ultramodern language: Slick, silver, nontransparent glass forms a gridded, reflective skin over a simple rectangular volume. Narrow green bands and thin dark joints provide ornamental relief. Then, leaving the warehouse's brick exterior essentially unchanged, the designers added an arcaded loggia and pilastered base of terra-cotta and green tile that skirts the bottom of new and old, linking them visually.

What next? Will styles now out of fashion eventually find a new audience anxious to revive them, or transform them? History suggests that it's only a question of when, not if.

NEXT: Beyond style -- back to the streetscape.