The Athenians gathered in an agora beneath the Acropolis, Romans in the Forum, and Renaissance men in a plaza cleared by the Medici merchants. Monumental structures of every age wax and wane, and the shopping centers that began springing up here in the 1950s and '60s are no exception.

Many Washington area malls are undergoing cosmetic surgery -- a skylight here, a paint job there, sunken amphitheaters and new "sculptures." Others are being expanded, and new tenants are recruited while old ones fail.

Development of new malls continues in spite of an established retail slump. One major trend is toward centers that are composed entirely of discount stores. Meanwhile, specialty shops imported from the streets of Europe and Beverly Hills are said to be waiting in line to sell to affluent Washingtonians.

What follows is a guide to local variations on one of the 20th century's prime gathering places -- the shopping center. Montgomery Mall

A Coldwell Banker leasing agent likened Montgomery Mall's current face-lift to home maintenance: "Every shopping center reaches a point where it needs redecorating, like a house." The agent also said the 14-year-old mall is one of the area's top three centers of its size.

The May Department Stores Co. of St. Louis, owners of Montgomery Mall, Parkington and the Hecht Co., is spending more than $2 million to "transform the mall's subdued appearance to a lighter, airy look," a company spokeswoman said.

The renovation involves the installation of a new floor and ceiling, high-intensity lighting, additional skylights and redesigned entrances. The mall is being repainted; its "sculptures" replaced with "contemporary" fountains, and a sunken auditorium installed. Tenants have been asked to remodel their stores.

"A tentative expansion" under consideration would add movie theater and fast-food facilities and a sit-down restaurant. The plan is a result of a May Co. study that found its properties to be "weak in food," the spokeswoman said.

In keeping with the study, the character of Montgomery Mall's stores will gradually change. "As leases roll over, we'll update the mix," the spokeswoman said.

The 44,000-square-foot expansion, for which no date for completion has been set, is expected to cost about $4 million. The mall's ongoing, more cosmetic facelift is scheduled to be finished by Thanksgiving weekend, the company said. Dobbin Center, Columbia Mall

Memco and Hechinger's are the "anchor stores" for Dobbin Center, a 246,000-square-foot mall being built in Columbia by Howard Research and Development Inc., a joint venture of the Rouse Co. and Connecticut General Corp.

Marketing manager Mike Krauss said HRD is trying to attract to Dobbin Center "quality, off-price" tenants in the clothing and home improvement market. The company hopes to have rented 85 to 90 percent of the space when the mall is completed in February, Krauss said.

Several "pad sites," or buildings standing alone on the center's parking lot, have been sold to First National Bank of Maryland and Wendy's, McDonald's and Friendly Ice Cream Corp.

Dobbin Center, which Krauss said is expected to draw customers from Laurel, Catonsville and Ellicott City as well as Columbia, has been planned as a supplement to Columbia Mall, where approximately 370,000 square feet were added about one year ago. The expansion brought a Sears store and about 55 specialty stores, and new entrances and store awnings were added. The Rouse Co. said about 94 percent of the mall's 900,000 square feet is occupied.

Each of the "villages" that make up the city of Columbia is equipped with a "village center." Krauss said none of these smaller convenience centers are being built now because "right now we're not at the level of population where development demands [more] village centers."

The Rouse Co. is currently involved in development of the National Press Building; Baltimore Center, a mixed-use project across from the Inner Harbor, and Painters Mill, a one million-square-foot shopping center northwest of Baltimore with tenants such as Garfinckel's, Woodward & Lothrop and Bamberger's. Rockville Korvette's Site

No name has been chosen for the Rockville Pike center that formerly housed a Korvette's store. But the discount spirit of the former tenants is being preserved with the location of such "off-price" tenants as Syms clothing, Scott's hardware, Bill's Carpet Warehouse, D&F Office Furniture, Toys-R-Us, the Gold Mine jewelry, Contemporary Sound audio and an as-yet unnamed discount ladies shoe store.

The leasing agents for the site's owners, Federal Realty Investment Trust, said other leases still being negotiated involve a gift store, a cafeteria and "a specialty, family entertainment restaurant." Germantown Commons, Montgomery Village, Lakeforest Mall, Fairland Fashion Center

About a month ago, Western Development Corp., builders of Georgetown Park, opened Germantown Commons, a neighborhood center designed for a community of 15,000 to 40,000 people. The mall has a Giant Food store that anchors 20 to 25 store slots, which the developers expect to finish leasing by spring. About one-half of these were occupied when the center opened.

The first shopping mall in Germantown, it was built on the assumption that the area will continue to attract "dual-income families" who commute to Washington, work at the Germantown offices of companies such as Fairchild and Comsat or go to school at the Montgomery College Germantown campus, according to Western suburban marketing director Patrice Kahane.

In Gaithersburg, Western Development is building Montgomery Village Fashion Center to house the discount stores Mandy's, Jay's Designer and Sassafras clothing, S&H Shoes, Linens 'n' Things, Crown Books, Trac Auto and off-price wallpaper, cosmetics and needlecraft outlets. A "small convenience row" next to the discount strip is designed to complement a Safeway store, according to Western partner Herbert Miller.

The fashion center is near Lakeforest Mall, which has over one million square feet of retail space. The developers of Lakeforest, the Taubman Co. Inc. of Troy, Mich., said about 90 percent of its space has been leased. No expansion or remodeling is planned.

Western Development also is building a similar off-price mall, Fairland Fashion Center, on Route 29 between Silver Spring and Columbia. Miller said the 200,000-square-foot center, scheduled to open in spring 1983, would be split between convenience and off-price stores. The company also began construction this month on a neighborhood center in Reston called South Lakes Village, which is similar to Germantown Commons. Laurel Centre

Because "what Laurel was like in 1960 is not what it's like now," Laurel Centre is being "re-merchandised," according to Coldwell Banker agent Mike Gorsage. J. C. Penney's, Montgomery Ward's and Hecht's have been signed as tenants. A Showbiz Pizza Place, a "theme restaurant" with entertainment and video games, will be complemented by a children's clothing store called Kids Unlimited. Other retailers, such as a self-service shoe store, a "sweets shop" and a toy store, will "help create a diversity," Gorsage said. Beltway Plaza

With tenants like Best Products, Marshall's, Luskin's, Pic 'n' Pay Shoes and K mart, the 1960s-vintage Beltway Plaza is working to place itself in the discount market of the 1980s, according to owner Sidney Brown. In addition, the Greenbelt center's facade has been redone at a cost of $500,000; construction will begin on an open auditorium in 90 days; eight movie theaters will be added to the existing seven, and Suburban Bank, Swensen's Ice Cream, Hickory Farms and a privately owned restaurant are planned. Wheaton Plaza

The mall has been enclosed, tenants have changed, and a grand opening to kick off Wheaton Plaza's new look is scheduled for the near future. But after taking over from the Lerner Corp., developers of White Flint and Tysons Corner, the new owners of Wheaton Plaza declined to comment on their new property. Crystal City Underground

The Charles E. Smith Cos. are moving to take advantage of what one associate called "a retailer's dream" in the Crystal City area: In addition to the 50,000 relatively affluent people who live and work in its 40 high-rise buildings , Crystal City Underground draws on a substantial tourist market using eight area hotels and National Airport.

The Underground's recent changes consist mainly of 25 new stores, including Casual Corner, Hess Shoes, Jay's Designer Discount, Crabtree and Evelyn, Ticketron and Radio Shack. The developers have upgraded the Underground's restaurant facilities with the addition of the Cookie Connection and French and Italian cafes.

Senior vice president Chuck La Pine noted that "in a year that has been terribly difficult for retailers, there has been a significant increase in sales at the retail level at Crystal City." Gross sales were $10 million in 1980, $12.5 million in 1981 and are projected to reach $20 million for 1982. Seven percent of the mall's 140,000 square feet remains to be leased. Parkington

Financing and design snafus have delayed the $100 million renovation of Parkington Shopping center, renamed Ballston Commons in a contest among Arlington residents. When completed in 1985, the joint Arlington County-May Co. project will include a three-level mall, a nine-story office building, a remodeled Hecht's and an enlarged parking garage. Woodlawn

A prefabricated, industrial-style "butler building" erected in 1974 on the Woodlawn Shopping Center parking lot is being blamed for the decline of the colonial brick mall on Route 1 in Mount Vernon, according to Coldwell Banker agent Tom Perucci. After suffering through problems that led to bank foreclosure, Woodlawn has been renovated with a new sign, a new roof and a new pad site occupied by Wendy's. Perucci said 101,000 square feet of the 105,000 total has been leased. Shirlington

The Oliver T. Carr Co. hopes to get Arlington County approval to build a $250 million mixed-use project near Glebe Road in Shirlington. The development's first phase envisions a $30 million renovation of the existing 28th Street retail strip "on a Main Street theme," with new facades, landscaping, lighting and sidewalks. Fair Oaks

The opening of Raleighs' 24,000-square-foot store is the most recent development in the Taubman Co. mall in Fairfax, where 86 percent of 1.4 million square feet has been leased. Georgetown Park

After leasing "virtually all of the space" in the luxurious Georgetown Park mall, which opened last year, Western Development is studying whether to proceed with its second phase expansion into an adjacent parking lot, said Coldwell Banker agent Gorsage. The company controls the property, he added.