IN THE 1960s, despite an outcropping of new buildings and widened streets, downtown Washington had a gray and aging face, showing increasing shabbiness and less of its former gentility. But now, years later, it was a colorful section of imaginative arcades, pedestrian promenades, stores, shops and caf,es. The pedestrian could wander around separated from traffic. People liked to look at displays in the merchandise mart or watch the excitement around the convention center.

"The Arena Stage, in the new Southwest, was flourishing. And the National Cultural Center on the banks of the Potomac offered concerts, operas, plays, recitals, and art shows. Because Washington was the Nation's Capital, citizens could see Russian and Danish ballet companies, French pantomime, African dancers.

"All these things were important to Washington area residents. They now had more leisure, more money, more education."

IF IT WEREN'T FOR the reference to the National Cultural Center, which actually became the Kennedy Center, you might not have guessed that this was a passage published in 1961.

Titled "Today's Dream Can Be Tomorrow's Reality," the article in The Washington Post was written as a projection into the future. Its accuracy is eerie.

Barring an immediate and almost total reversal in economic conditions, what will happen to center city Washington over the next decade will be truly astounding, visually and environmentally.

Buildings designed by prize-winning architects; new movie theaters, cabarets, saloons and restaurants -- an entirely new life will come to the downtown area.

THE DISTRICT OF COLUMBIA'S downtown building boom started in earnest as Metro trains began running in 1976.

Still, it was five more years before the start of the gold rush that is now turning the remains of the old downtown -- from 14th Street to Judiciary Square -- into a vibrant, gleaming new downtown.

Since 1961, buildings have been completed or are under construction on every single square block of the center of downtown, between 10th Street and 15th Street, all the way from Pennsylvania Avenue to K Street.

The massive investment in downtown has been made possible by an improving economy; by creation of the Pennsylvania Avenue Development Corp., the federal agency set up in 1972 to engineer the revitalization of the nation's main street; by the city's priority in refurbishing the downtown area; and by the opening of the convention center.

But what may determine the ultimate character of Washington's new downtown is one little-noticed trend that began in 1980. Several of the nation's largest developers -- who had never done any projects in Washington before -- decided the time had come for them to make their mark here.

These developers differed from home-grown builders: they tended to spend more to design and construct high- herefore charged top-of-the-line prices for leases.

Historically, there has been little or no demand for such buildings in Washington. In effect, the city has gotten what it has paid for: rows of square, relatively uninspired office buildings that went up quickly and cheaply.

Credit for shooting the starter's gun in the downtown stampede goes to Cabot, Cabot & Forbes and its client Covington & Burling, the law firm that opened the 1201 Pennsylvania Ave. office building in 1982.

Not far behind was the law firm of Hogan & Hartson, which agreed shortly after to become the prime tenant in the behemoth Columbia Square, designed by I.M. Pei & Partners and built by Gerald D. Hines Interests Inc. of Houston, which is now rising on F Street between 12th and 13th streets.

Columbia Square will be constructed almost entirely out of expensive Stoney Creek granite. It will have bronze and mahogany elevators and a stunning 13-story glass atrium, which allows it to give Hogan & Hartson and the several other law firms it hopes to attract, something very important.

"Windows," said Hines' vice president Bill Alsup. "Lawyers love offices with windows."

On the ground floor will be upscale shops. Hines is cooperating with the city's long-term plan to turn F Street into a boutique shopping street resembling New York's Fifth Avenue or Madison Avenue.

Washington has already had marked success in bringing a revitalized retail business to downtown. The conversion of the Old Post Office into an inner-city mall of boutiques and restaurants and the opening of the Shops at National Place diagonally across Pennsylvania Avenue were followed by the opening of the lavish ne Hecht's on G between 12th and 13th streets.

If the Hecht's store -- the first free-standing downtown department store to be built in a big American city in 40 years -- is any indication of what is to come, city officials have every right to be optimistic.

According to Hecht's president Irwin Zazulia, the store did 35 percent more business than planned during November, its first month of operation.

Attempts are also continuing to bring Bloomingdale's to the neighborhood.

The Hines vice-president said his firm likes to build expensive buildings for a number of reasons. While the initial profits to investors in higher-priced buildings are lower than average, the long-term profit yield is much more consistent. Expensive buildings stay filled. Foreign investors like to put their money in quality ventures, Alsup said, and prefer to take a longer view.

And, he added, when the market softens for a time -- which it inevitably does -- expensive buildings are generally the last to be adversely affected. Quality tenants prefer to stay in quality buildings. It also helps to have one client occupy almost half the building.

John Shooshan, a vice-president of Cadillac Fairview Urban Development Inc., whose building sites include 1001 Pennsylvania Ave. and 13th and K streets, said that his firm was attracted to Washington because of the unique stability that the federal presence lends to the city, and because of the presence of lawyers, trade associations and accounting firms (the "three As to the real estate industry: Attorneys, Accountants and Associations"). His firm regards Washington real estate as "blue chip stock."

The rush to build has its drawbacks, of course -- vacancies. Alsup's firm is predicting that the office vacancy rate in downtown will hit 6 percent by early this year (more than twice last year's rate), and may reach double figures by the end of 1986 -- although, according to Alsup, these rates are still good when compared with national vacancy rates.

HINES AND THE OTHER big-ticket builders aren't the only ones in the top-of-the-line market these days. Washington area developer Oliver T. Carr is asking for -- and getting -- about $35 per square foot for leases in the Willard office building, which is being constructed in tandem with the renovation of the Willard Hotel. Carr's Willard rate is the highest in the area, but others are competing closely with it.

But though bright new office buildings may generate hustle and bustle during work hours, they tend to create an almost ghost-town atmosphere during evenings and weekends. Consequently, residential housing has been the focus of much of the downtown development. If people live in the newly refurbished neighborhoods, they will encourage the operation of movie theaters, grocery stores, caf,es and restaurants.

The original charter of the Pennsylvania Avenue Development Corp. included a proviso for 1,500 housing units, with 300 set aside for units of "moderate" cost. In 1981, those 300 units were eliminated from the plan.

But the current chairman of the PADC, Henry A. Berliner Jr., has set 1,500 as his personal goal. And though he acknowledges that property values on Pennsylvania Avenue will probably preclude any moderately priced housing, he points out that PADC territory goes as far as four blocks from the avenue, and can include more affordable units.

Executive director of the PADC, M. Jay Brodie, points to the Westminster Investing Corp., which has twin buildings on land at 601 Pennsylvania Ave. The first building, which is under construction, will have office and retail space; the second, due to be started in early 1986, will have a hotel and 200 rental units. The Market Square project of Western Development Corp. and Kan Am Realty Inc. includes 225 residential units. The prospectus for the Lansburgh's Department Store site between Seventh and Eighth and D and E streets NW, includes plans for 225 more units. "It's a start," Brodie says.

Art Schultz, founder and executive director of the Franklin Square Association, said the lack of housing is "the sad thing" about downtown. Residential building is "just not economically feasible," given current economic conditions and the rent control laws in the District. Developer Jeffrey Cohen, who has sold his downtown properties to concentrate on a city-sponsored project in the Shaw area of Northwest Washington, doubts that housing will be a substantial element in downtown, because government -- both city and federal -- currently provides too few financial incentives for the development of housing.

But if residents don't have places at or near downtown for a while, visitors certainly do. Recently opened hotels include the J.W. Marriott, the Vista International, the Henley Park, the Phoenix Park, the Sheraton Grand and the Park Terrace.

And according to the Washington chapter of the American Hotel and Motel Association, hotels in the planning or construction stages include the Holiday Inn Crowne Plaza at 12th and H streets, the Grand Hyatt at 10th and H streets, the Morris and Clark at 11th and L streets, the Comfort Inn at Fifth and H streets, and the Willard Hotel on Pennsylvania at 14th Street and the Ramada Renaissance at Ninth and I streets. (The Ramada Renaissance is part of developer Giuseppe Cecchi's Techworld, a $250 million high-tech trade center designed to attract companies involved in contracts with the federal government.)

With good occupancy rates, hotels will bring to the downtown area thousands of guests whose meeting and convention schedules will leave them with free evenings. And although hotels have proliferated in recent years, the business, government and convention attractions of the city seem to be supporting them. Wesley Ayre, director of leisure time services for Laventhol & Horwath, an accounting firm that tracks hotel trends, said that for the first nine months of 1985, occupancy rates in the District were 73.4 percent, an increase of four percent from 1984. The average room rate was $88.52, up 12.9 percent from the same nine months last year. As of December 1985, there were 67 hotels in Washington, with a total of 18,509 rooms.

Downtown guests and residents can enjoy access to the performing arts, with the National, Warner, Studio, Source and Ford's theaters nearby. And Ted and Jim Pedas, owners of the Circle Theater chain, have bought 23,000 square feet at the southeast corner of Ninth and H streets, and plan to start building an eight- screen theater in two or three years.

The determination to have shops and movies and housing interspersed with the office buildings and hotels is part of the drive of the District of Columbia Downtown Partnership, whose co-chairmen are Oliver T. Carr and Curtis McClinton Jr., deputy mayor for economic development. Prtership Director Ellen M. McCarthy said, "It is a cooperative effort of government and business, aimed to harness the energy of downtown development, so that Washington guests and residents can live, work, shop and be entertained downtown." This year, for the first in 20, downtown street lights were decorated for the winter holidays, thanks to the Partnership.

Full confidence in the downtown is a fairly recent occurrence. Memories of the 1968 riots, of prostitution, pornography, drugs and crime clouded the view of developers looking east toward the Capitol. But now the strip of porn shops on 14th Street has been eviscerated. The Franklin Square Association was instrumental in helping to close these businesses, hiring private detectives with hidden cameras to find activities that could be protested before the Alcoholic Beverage Control Board. And tantalizing dollar figures tempted the owners of the buildings to sell to developers rather than renew leases.

Now, Texas-based Trammel Crow Co. holds the land that once housed Benny's Home of the Porno Stars, The Californian Steak House, the Gold Rush, and the Cocoon and Butterfly clubs. Trammel Crow has also purchased Campbell Photo, the Parkside Hotel, the American Youth Hostel on I Street and Popeye's Fried Chicken at 14th and I streets. It plans to build a 12-story, 350,000- square-foot office building overlooking Franklin Park.

Along with its gloss and newness, the area has its convenience to the Mall, Capitol Hill, Chinatown, Metro, Union Station and I-95. Brodie stresses that Washington is the national capital, a special place for Americans who will visit because of the national monuments, museums and government institutions. And these visitors will find abundant shopping, dining and entertainment just footsteps away.

"You are seeing the suburbanization of downtown," said Mo Sussman, owner of Joe and Mo's restaurant on Connecticut Avenue. "It is to be spectacular."

STILL, the great eastward motion continues. Prospects look good, movement is fast, the mood is upbeat. To paraphrase the title of the Maurice Hines musical that previewed recently at the Warner Theatre: "Downtown . . . It's Hot."