From Trastevere and Montmartre to Greenwich Village and Soho, artists, by their very presence, have been upgrading broken-down neighborhoods for centuries.

Could downtown Washington be next?

The forces for such transformation have been gathering since the arrival, a decade ago, of two major museums downtown -- the National Collection of Fine Arts and the National Portrait Gallery.

With the Martin Luther King Library and the old Mickelson Gallery, these institutions have been lone outposts until the recent launching of a satellite gallery scene downtown, now numbering several establishments, many of them artist-run.

The proposed "Gallery Row," a commercial complex of gallery and studio space is being planned a few blocks away.

But there have been for many years other cultural riches downtown which few Washingtonians have known about -- namely dozens of artists (possibly hundreds, no one really knows) who seem to occupy ever deserted urban building that has high ceilings and low rent.

These hidden assets are about to be revealed, at least in microcosm, in Washington's first "Open City," when 20 artist's studios are opened to the public over the next three weekends, starting today.

"I want to develop the energy downtown and keep it going," says A1 Nodal, the Cuba-born, California-bred new director of the Washington Project for the Arts (WPA) who masterminded the event. "I want to let people in various neighborhoods know that there are artists living and working among them, not just showcasing in galleries."

Nodal hopes to make "Open City" an annual affair as are similar open-studio days in New York, San Francisco and Boston. Though several Washington artists have opened their studios on an annual basis in recent years, usually before Christmas, there never has been a coordinated effort involving so many artists here before.

Nodal, along with some of the artists involved, admits some disappointment that more "well-known" names are not included on this year's list. "But that will come if we succeed."

Manon Cleary, Nade Haley, Michal Hunter, Rick Ward, Stephen Ludlum, Alex Jamison, Genna Watson and John Dickson are among the artists whose names might be more widely recognized. But well-known or not, artists always make interesting company, especially in the presence of their work.

Although sales are possible, they do not seem to be the chief concern. "Events like this generate creative energy," said sculptor Nade Haley, "and you never know what this can start."

That goes double for those who take the trouble to go out and have a look, not only at the art and the artists, but also at some of the best studio space in town, including the Johnson Avenue Workshop, former studio of Sam Gilliam and Rockne Krebs, and the Le Droit and Atlas Buildings across the street and around the corner from the National Portrait Gallery.

A sensible itinerary might begin at WPA, 1227 G. St. NW, (open today and tomorrow noon to 5 p.m., but on following weekends closed on Sunday). For, in addition to mobilizing the city's artists -- something WPA has attempted to do since it began, Nodal also has brought some expansive new ideas to WPA, along with a fresh coat of paint.

Nodal has divide the space into three discrete areas so that three different shows can go on simultaneously, also adding a fine little book stall featuring small-edition, artisti-made books, the only place in town where they currently can be found. Some time should be left for a good browse.

The featured exhibition at the moment is called "Contemporary Washington Artists," new works by artists who have shown solo at WPA over the past five years. A lyrical piece made of delicate wood elements by John Dickson islikely to lure viewers to that artist's Johnson Avenue Workshop. Nade Haley, likewise, can be seen in both places.

There are also a power ful sculpture of natural wood and steel by David Staton, photographs by Bernis and Peter von zur Muehelen, and two poignant and delightful notebooks by Terry Braunstein, including her longest work to date, entitled "Sex." Budget some time for this one.

In another gallery, several political, phiosophical and funny drawings by California artist-writer Ken Friedman are on view.

But of particular interest to Washingtonians who have been frustrated in their attempts to get an overview of contemporary video art, is "Continuous Video," a continuous screening of several recent tapes by artists from all over the country, through Feb. 15.

And on the subject of video, three of the best artists in the field will be performing, in person and/or on tape at D.C. Space, upstairs over the health-food restaurant and artist's bar at 7th and E Streets NW, starting with Eleanor Antin on Wednesday, Vito Acconci Thursday, and Dennis Oppenheim Friday, all at 8 p.m.

In addition to the artist's studios on the "Open City" roster, there are several nearby gallery shows, including "A Woman's Perspective," at Miya Gallery, 720 11th St., work by two black women, photographers, Stephanie Sheppard and Jo Ann Henry, through Feb. 7.

And the Le Droit Building at 802-810 F St. NW, just opposite the National portrait Gallery, is featuring both a show of "Studio Women Past & Present" and several open studios, although one of the best painters and printmarkers in the building, Frank Wright, is not on the roster. A knock on the door of his studio, first floor, turn right, could provide a highlight of the day. If he happens to be there, he has promised to welcome visitors.

If now, Wright's recent paintings of downtown Washington, must apropos in this context, are currently on view in another brand new downtown space provided by the Pennsylvania Avenue Development Corporation in the Willard Hotel, corner of 14th and F Streets, NW.

Included are some of the artist's best paintings to date, notably several scenes of the inside and outside of the Le Droit Building, as well as reconstructions of some great parades that took place on Pennsylvania Avenue in the 1880s.

Back at the real Le Droit Building, or just around the corner, the Atlas Building at 527 9th St. NW and another building at 930 F St. NW, there also will be open studios. Just a few blocks further on, at 641 Indiana Ave. NW. Intuitiveye Gallery is showing three photographers, including the sensuous and intriguing work of Robert Cree.

In addition to the Johnson Avenue Workshop, at the rear of 1737 Johnson Ave., between R and S Streets NW) which should not be missed, there is another clutch of galleries and studios on and near Columbia Road NW, where Manon Cleary's studio, Madams Organ Gallery, 2318 18th St. NW, and one of the best new gallery spaces in town, the Felluss Gallery, 1800 Belmont Rd. NW, are located. Local 1734, at 1734 Connecticut Ave. NW, is also participating, currently featuring a show which is chiefly "Blue," which also, appropriately, is the title.

There is much more that will no doubt turn up along the way, and those who set out to explore "Open City" are advised to first pick up a list of participants and locations at any of the participating galleries or at the Corcoran. Since hours vary, (though most are open from noon to 5 p.m.) and some artists request a phone call in advance, locations and times shoud be carefully noted and checked before setting out.