"There's nothing up there except a storage room," shrugged the waiter at the elegant Da Vinci Ristorante, following our eyes toward what used to be the third floor. A skylight had been cut through the roof and what had been two floors of apartments above a bar were now balconies looking down on the chic main dining room.

As we sat on the banquettes enjoying fettucine verdi da Vinci with cappucino pie for dessert, we remembered when the ground floor at 2514 L Street NW was a Greek bar and grill called Mellones' and the upper floors, known to the postman as 25141/2, held a rabbit warren of apartments sublet to a variety of tenants by a young man from India pursuing an elusive graduate degree. This was twenty years ago, when my now- husband was one of those tenants.

Nothing stays the same for twenty years, and Washington's West End, roughly defined as the area skirting Pennsylvania Avenue from 20th Street to Georgetown, has changed considerably since we first came to town. Some of it, such as the old Western Market, regrettably has vanished, but other spots have changed for the better. The West End, as we recently rediscovered, still is a lovely section with many places to browse, stroll and eat.

From an urban-design point of view, the focal point of the neighborhood is Washington Circle, one of the devices L'Enfant used to ease the intersections of major thoroughfares -- in this case Pennsylvania and New Hampshire Avenues. L'Enfant could not have foreseen the current level of traffic, which now makes almost inaccessible the green patch with the equestrian statue of Washington at its center. The bronze statue by sculptor Clark Mills was dedicated February 22, 1860, in a ceremony attended by le tout Washington. According to historian Constance McLaughlin Green, the statue helped ease the city's frustration over the uncompleted obelisk on the Mall, on which work had halted in 1855 for lack of funds and other problems.

On the northeast side of the circle between K Street and New Hampshire Avenue stands the Schneider Triangle, a cluster of dark-red brick rowhouses in the brooding Richardsonian style by Cairo Hotel architect T. F. Schneider. Across New Hampshire, in the basement of an undistinguished high-rise apartment house turned hotel, is one of the small restaurants that make the West End so much fun: The WEST END CAFE. It actually is two rooms, both surprisingly light and airy for a basement and one with an undulating bar, separated by a lobby decorated with blown-up photos of the neighborhood, The decor runs to burlap-covered walls and tapestried banquettes and linen and fresh flowers; the menu runs from ceviche to frozen Amaretto souffle.

Completing the northern half of the circle is a brownish-red neo-Victorian cluster of medical and residential condos, the result of a compromise between preservationists and a developer who wanted to tear down the turn-of-the-century homes on the circle and put up a nondescript highrise. Preservationists got the houses declared landmarks. After many hearings and meetings, a compromise was worked out whereby architect Guy Martin designed a smaller structure that incorporated some of the old facades, but the delays and changes may have contributed to the developer's bankruptcy. The building now has only one residential tenant, who is currently suing the bank that took over the building.

The Dutch roofed houses just past the circle on Pennsylvania Avenue may have given e the Washington Circle area its 19th century name, "Round Tops," although the name also referred to a gang that gave the neighborhood a bad reputation.

The 2400 block of Pennsylvania is in transition. An unusual, vaguely nautical building has replaced many of the old apartments-over shops. Behind, where L Street runs toward Pennsylvania, looms Columbia Hospital for Women, established in 1866 as a "lying-in asylum" for those who couldn't afford private care.

The 2500 block is more fun, housing four interesting restaurants. LA SORBONNE, at 2507, has unfortunately closed its wine bar, but still is a pleasant outdoor-indoor cafe with food and ambience worthly of its name. Try the ratatouille with scallops when it's on the luncheon specials ($5.50). La Sorbonne also serves Sunday brunch, as does its neighbor, the ONE STEP DOWN LOUNGE. At 2519, MAXINE'S advertises "Swiss cuisine, American bar," and the establishment's dual citizenship shows on its exterior, a Victorian townhouse draped with a Swiss flag. It's tempting to sit outside and eat such specialities as cauliflower soup and schnitzel with fried egg and capers, but be sure to peek inside at the opened-up townhouse's beautiful dining room downstairs and antique bar and oak-manteled fireplace upstairs. Next door, MARSHALL'S WEST END, also in a red-brick Victorian, features such fare as sole Florentine, Reubens and omelets.

The Westbridge, an office and condominum building at 2550, has wraparound balconies that overlook Rock Creek Parkway and Georgetown. The Westbridge replaces Thompson's Honor Dairy, which once supplied milk to the city and later became an abandoned building that neighborhood kids called "the scary dairy."

From here, it's tempting to cross the bridge into Georgetown, but if you resist you'll discover some of the less-heralded charms of the West End. Cross to the south side of Pennsylvania, glancing at the service station on the corner of 26th Street just long enough to mourn its predecessor, which was in the Historic American Buildings Survey.

There still are a few 19th century houses left where L Street turns the corner onto 26th, a quiet oasis facing a small park overlooking a maze of freeways. The short block of L that leads toward Pennsylvania also holds three eating and drinking establishments. At 2524 there's BAKER BROWN'S, which under the previous administration was Sarsfield's, where White Houser Hamilton Jordan allegedly spit Amaretto-and-cream. At 2514 there's the aforementioned DA VINCI'S, and right next door there's WHALER'S, which boasts a raw bar.

Back on Pennsylvania Avenue, across 25th Street from the new Guest Quarters, stands the Roman Catholic church of St. Stephen the Martyr, adorned with a large statue of the saint. The church enjoyed a burst of fame in the '60s, when President John Kennedy occasionally drove up the avenue to attend Mass. A century before, St. Stephen's was a stronghold of the Irish Catholics who lived in Foggy Bottom and worked at the Washington Gas Light Company's plant on the river. On paydays Pastor John McNally used to stand outside the plant to collect contributions to finance the church, built in 1868. The neo-Gothic building, by architect Adoph Cluss, who also designed Eastern Market and the Franklin School, was replaced by a rather uninteresting structure in 1959, but the original rectory remains.

The supermarket and drug store on the same block also have long served the neighborhood; now, however, their wares are hidden by curtains on the display windows.

"The landlord wants it that way so it will look like the hotel," explained one of the clerks, referring to the adjacent apartment building-cum-hotel.

George Washington University Hospital fronts on the south side of Washington Circle. A few doors down, at 21381/2, the TRIESTA, a West End institution, serves its spicy, garlicky pizza and other Italian fare in an informal resturant often packed with families, including the owner's. The signed photos of Washington notables on the wall are the same; only the building's facade has changed in the past twenty years -- from fake stone to real brick.

A Blimpie's men's store and a MR. HENRY'S occupy a row of small buildings on the block, which ends with the massive Joseph Henry Building, built by GWU as an investment. Although the building is characterless, it houses a West End institution: REITER'S STUDENT BOOK COMPANY, which stocks texts on everything from agriculture to Zen and has an active bulletin board for the student community.

Across 21st Street, in the 2000 block of I Street, which faces Pennsylvania across a small triangular park, a more interesting university building is taking shape. After years of public hearings, court battles and negotiations, the university is saving at least the fronts of the 19th-century homes on the block and incorporating them into a new building which will be a gateway to the campus. The Red Lion Pub, which gave the block its unofficial name of Red Lion Row, is gone, but if you want to sit in the park and watch the construction, you can still choose from 20 kinds of hamburgers at the BON APPETIT carryout at 2040 I Street.

At 2001 I Street, across Pennsylvania Avenue and a matching triangular park, stands the FRANZ BADER GALLERY AND BOOKSTORE, a browser's delight. The book section holds tomes on every aspect of the arts, from coffee table books on American Impressionists to paperbacks on how to make Mission furniture, works on every subject from the monasteries of Western Europe to Japanese bamboo baskets. Shows in the gallery change frequently and range from one-artist exhibits to mixed-media group shows. Franz Bader regulars include such popular local artists as Dora Lee and Alice Acheson.

Doubling back toward Washington Circle, close your eyes as you pass a couple of rather bleak office buildings, and open them up at 2017 I Street for a look at THE ARTS CLUB OF WASHINGTON. Founded in 1916, the club occupies the Timothy Caldwell house, built in 1805 in the Federal style. If you're a member, you may lunch in the dining room on Wednesdays and sip sherry in the library before the formal Thursday dinners. The rest of us can just walk in during the regular exhibit hours (2 to 5 Wednesdays, 10 to 6 other weekdays, 1 to 5 weekends) and enjoy frequently changing shows and admire the landmark house. President and Mrs. Monroe lived here for several months in 1817, while the White House was being repaired after the British burned it, and the triangular park is actually ''Monroe Park." The doorway and its fanlight are notable.

Not as old as the Timothy Caldwell house but still a venerable cultural landmark is the CIRCLE THEATRE at 2105 Pennsylvania. The Circle features double features and a subscription book of 10 tickets costs what we used to pay for it twenty years ago: $10.

For a beer and sandwich after the movie, the 21st AMENDMENT, half a block away at 2131 Pennsylvania, will do nicely. For something more formal there's LE GAULOIS next door, with such changing specialities as duck with kiwi fruit and fruit tarts.

If you're interested in food for thought, browse through the MOONSTONE BOOKCELLAR, one flight down from Puglisi's Barbershop at 2145 Pennsylvania. The Bookcellar specializes in science fiction, fantasy and mystery and includes such diverse selections as The Celebrated Cases of Judge Dee, "an authentic 18th century Chinese detective novel," Peter Pan, and A Child's Garden of Vampires along with the fireworks of Arthur C. Clarke and the mysteries of Ngaio Marsh. There is also a large selection of fantasy newsletters.

Time was, every neighborhood had its pawnshop, and the West End still has one: S&W LOANS AND LUGGAGE at 2157 Pennsylvania. The traditional three balls here are rendered in neon, and the window is chock-full of pawned goods: "genuine diamond" rings, watches, binculars, cameras and typewriters.