THE WINNER of Tuesday's sweepstakes can look forward to a limousine ride along Pennsylvania Avenue from the White House to the Capitol and back again.

A couple of decades ago, that ride wasn't considered a major presidential perk. In fact, President John F. Kennedy's remark that the scenery along his inaugural route was pretty dreary spurred the spiffing up of the avenue. Today, Pennsylvania Avenue is not only a stately boulevard, but also a fun place to eat, drink, shop, play tourist, ice skate, play chess, watch a hit play, absorb art, commune with dead heroes, browse among antiques, view what may be the world's oldest elevator, trace your roots, watch the sharks eat, relive the Battle of the Argonne, soak up history or just watch the passing parade.

Pity the poor president-elect. He'll be too busy waving to the crowds to really enjoy Pennsylvania Avenue. Anyway, he'll be making the trip in cold, cruel January. You, however, can tour the avenue this weekend -- or any weekend. Start, like him, at the White House and eat, drink, gawk and play your way to the Capitol. (The best part is that when you get there you won't even have to make a speech.) THE PRESIDENT WHO BLOCKED THE VIEW AND THE GENERAL WHO WOULDN'T BE PRESIDENT

You won't get a glimpse of the grand sweep of the avenue until you get around the Treasury Building, and that's the fault of an earlier president, Andrew Jackson. Old Hickory had appointed a committee to find a site for the building while preserving the view from the White House to the Capitol. Exasperated by their interminable indecision, Jackson walked out of the White House one morning, planted his cane in the ground and said: "Right here is where I want the cornerstone."

The sandstone and granite Greek temple, which has a statue of Secretary of the Treasury Albert Galltin in front and a statue of Secretary of the Treasury Alexander Hamilton in back, isn't open to the public. You can, however, get into the splendid, two-story marble and bronze Cash Room if you say you want to buy a Treasury bill ("Just bring ten thousand dollars and we'll let you in," joked a switchboard operator.) And, on weekdays from 9:30 to 3:30, you can visit the small museum with an entrance on East Executive Avenue. There are exhibits on Fort Knox and other chapters in the history of money. For $1, you can buy a pewter disc and watch it being stamped before your eyes with the White House on one side and the presidential seal on the other. As you round the building and head down 15th Street, note the plaque that marks the spot where the Webster-Ashburton Treaty, marking the boundary between the U.S. and Canada, was signed in 1842. (Actually the treaty was signed inside the old State Department building that used to sit on this site.)

Amble across 15th Street to the latest incarnation of the saloon reportedly frequented by Presidents Grant, Andrew Johnson, McKinley, Theodore Roosevelt and Harding. The Old Ebbitt Grill those worthies tippled in was actually around the corner on F Street, but the spirit -- or spirits -- of the place have been reborn in the Metropolitan Square development on 15th Street. William E. Ebbitt bought a boarding house on the edge of what is now Chinatown in 1856. A decade or so later he was emphasizing the saloon aspect of the business in a hostelry on F Street, which was taken over by Clyde's in 1970. Now the space is new but the ambiance is Edwardian, with real gaslights, hunting trophies hanging from the walls, huge silver vases filled with fresh flowers, green velvet banquettes and lots of dark wood. It's open from breakfast until after midnight and serves everything from oysters (Pine Island bluepoint, Louisiana Gulf, Chesapeake, York Harbor Belon, Prince Edward Island Malapeque) to hot fudge sundaes. Next door is the empty space where the venerable Rhodes Tavern once hosted the British who burned of the White House, and across F Street stands the Washington Hotel. Note the terra cotta reliefs on the outside and the classic turn-of-the-century lobby, complete with heavy, Empire-style furniture, elaborate plasterwork, potted palms and a polished brass cash cage.

You can get a pretty good idea of the view that Jackson's Treasury blocked by climbing up the steps of the General William Tecumseh Sherman Monument, just behind the Treasury Building at the point where 15th Street runs into Pennsylvania Avenue again. The site for the monument -- which consists of an equestrian statue of Sherman, allegorical tableaux of war and peace and four life-size bronzes of soldiers representing each branch of the army (infantry, artillery, cavalry and engineers) -- was selected because Sherman once stood there to review returning Civil War soldiers in 1865. Sherman might have lived nearby in the White House had he not delivered what is still considered the definitive political refusal: "If nominated, I will not run. If elected, I will not serve." PLAZA HOPPING FROM PERSHING TO PULASKI; AND DO YOU KNOW WHERE OUR SISTER CITY IS?

Pershing Park just across 15th Street is dedicated to a later war hero, Gen. John J. Pershing. There's a bronze statue of "Black Jack," detailed down to his spurs, and a marble map of the western front that gives a capsule history of World War I. On the lighter side, the park has a mini-lake that turns into an ice-skating rink in winter and it has a kiosk where you can buy light refreshments. Hidden in the trees is a bronze bald eagle, courtesy of the Audubon Society.

Facing Pershing Park stands the Willard Hotel, designed by Henry Hardenburgh, architect of New York's Plaza Hotel. The Willard, which closed in 1968 and is scheduled to reopen in 1986, hosted Lincoln, the Buchanans, Mark Twain, Nathaniel Hawthorne and Henry Stanley (sans Livingstone). Jenny Lind sang there. Julia Ward Howe wrote "The Battle Hymn of the Republic" there. Coolidge camped out there while he waited for Mrs. Harding to move out of the White House. The Willard brothers, Henry and Edward, opened Willard's City Hotel in 1850; the present building opened in 1904. While the renovation is in progress, you can glimpse the hotel's past grandeur and grand guests in an exhibit of poster-size photographs mounted on the construction fence.

On the other side of Pershing Park, across E Street, is the Department of Commerce building. With 37 acres of floor space, it's about the size of a modest farm, and the main crop is bureaucrats. Some of the acreage is of more general interest, however. On the E Street side, there's a tourist information center where you can pick up free brochures (including "A Walker's Guide to Pennsylvania Avenue") and buy souvenirs and folk art. And the 14th Street entrance leads past the ever- ticking population clock to the National Aquarium, where you can see a thousand specimens in 65 eye-level glass tanks. It's open 9 to 5 every day except Christmas. Admission is $1 for adults, 50 cents for children.

Right next door, across 14th Street, stands the District Building, a six-story marble wedding cake adorned with 28 draped male and female statues representing arts and enterprises in the District of Columbia. The District Building, which dates from 1908, was once scheduled to be torn down because its architectural style clashed with that of the other buildings in the Federal Triangle. Be sure to climb the steps at the front of the building to the elaborate oak doors that are opened only on ceremonial occasions. At the top of the steps is a gilded bronze bell presented by the people of our sister city, Bangkok. (If you don't think the two places have much in common now, wait until August.)

The District Building faces the vast, windswept Western Plaza. Most of the interest here is on the ground, where maps and sayings about Washington are etched in granite and marble. The sayings are by such notable and obscure people as Jefferson, Emerson, A. Maurice Low, Wilson, Martin Luther King Jr., Herbert Hoover and Sharitarish Pawnee. The quotation for this weekend? Try this one by Walt Whitman: "The sum of all known reverence I add up in you whoever you are: The president is there in the White House for you, it is not you who are here for him." At the eastern end of the plaza, Brigadier General Count Casimir Pulaski sits astride his bronze horse. Although he was commissioned in the Continental Army during the Revolution, he preferred to wear the uniform of a Polish marshal. And when the wind whips across Western Plaza, his Russian style hat probably serves him better.

On the north side of the plaza is National Place, consisting of the J.W. Marriott Hotel, a multi-level shopping and eating mall and the refurbished National Theater. The theater, Washington's oldest thespian institution, has played to audiences on this site since 1835. (Free tours of the newly renovated National are given Monday mornings at 11 for groups of six to 12. Volunteers regale visitors with the history of the theater, point out the renovation work, take you backstage to a costume and wig room and, sometimes, let you peek at a rehearsal. Book tours in advance by calling 783-3370).

Enter the complex through the hotel lobby on the corner of 14th Street and feast your eyes on its spectacular art deco rugs in luscious shades of lavender and mauve. Then wander downstairs, pausing for refreshment in one of the hotel restaurants (The National Cafe, the S.R.O. deli restaurant, The Celadon for French-Oriental cuisine or the Garden Terrace for cocktails) or just for a rest on one of the sofas, and gradually make your way into the chic, three-level shopping mall known as "The Shops." The shops sell everything from sensible shoes to nautical curios to silk-screened T-shirts to designer bodysuits. (If you have kids, you'll end up at Only Happiness, a sticker and novelty store.) Scattered among the boutiques and concentrated in the top floor Food Hall are 22 carryouts -- with central seating available so you can mix cuisines. Try a croissant from Au Bon Pain, a bagel from Bagel Place, boardwalk fries from Boardwalk Fries, a yogurt and fruit concoction from Everything Yogurt/Bananas; a giant chocolate chip cookie from Hershey Cookies; some batter-fried veggies from Incredible Vegetable; gourmet popcorn from Jack's Corn Crib; a stuffed potato from Stuft Potato; clams on the half shell from The Boston Seafood Company; and some toffee from Thornton's English Chocolate Shop. Don't worry about your weight. You'll walk it off by the time you get to the Capitol. FROM THE NEW POST OFFICE TO THE 'NEW' OLD POST OFFICE

Since they were going to tear down the Old Post Office, they built a new one, in 1934, with a neo-classical facade and a red tile roof just like the old buildings of the Federal Triangle. The new Post Office Department Building, on the south side of the avenue between 12 and 13th streets, has a floor plan in the shape of an hour glass. The part of the hour glass facing 12th Street forms a half circle. The half circle was supposed to be completed and turned ito a circular plaza when the Old Post Office Department Building was torn down.

The "new" Post Office Building also houses the Benjamin Franklin Postal Station, whose walls hold two murals painted under the New Deal program to keep artists off the dole. One painting, "The Family Letter," shows a little girl writing a letter while her brother teases the cat and her mother holds the baby. The other depicts a scene in a Civilian Conservation Corps camp: "Worker in Camp Reading Letter from Home While Other Workers Discuss a Point About Surveying." Both are by Alexander Brook. There's also a seven-foot marble statue of Benjamin Franklin by William Zorach.

Another statue of the former postmaster -- this one in bronze by Jacques Jouvenal -- stands just outside the newly renovated Old Post Office Building just across 12th Street. This building, in the Richardsonian Romanesque style, was out of date almost as soon as it was completed in 1899, in the midst of a vogue for neoclassical architecture. Almost as soon as it opened, it was marked by tragedy: City Postmaster James P. Willet fell through an unguarded elevator door and was killed. The Post Office Department abandoned the building when the new edifice next door was completed in 1934. The Old Post Office was almost sacrificed to architectural conformity and the plan for the Federal Triangle, but preservationists and people who wanted to bring new life to the avenue prevailed.

Enter through the 12th Street steps and look immediately to your right. Just to the right of the office door you'll see a sleek tabby cat, four feet high, formed by the blue veins in the marble. On the other side of the door, less well defined, is a shaggy Borzoi dog. Once inside, you can eat on either Main Street (chili, fries, beef, ice-cream, etc.) or Embassy Row (Chinese, Mexican, Italian or Indian cuisine), buy a scoop of sequins for 85 cents at Have a Heart, sip a margarita at Blossoms, try on haute couture, brunch at Fitch, Fox & Brown, quack at the ducky stuff at the Upper Duck, browse in a bookstore, pet stuffed animals or get ready for Santa at Christmas in Washington. You can also watch an occasional show on the stage and mount the 315-foot tower for a spectacular view, inside and out. THE HOUSE THAT HOOVER BUILT; ART, ARTIFACTS, ANTIQUES AND WORLD'S OLDEST ELEVATOR

The heavy, fortress-like J.Edgar Hoover FBI Building, on the north side of the avenue between Ninth and 1Oth Streets, isn't the prettiest new building on Pennsylvania Avenue. But don't look at the architecture -- look at the flags hanging from the facade. The flags on each end are current U.S. flags, and the ten in between illustrate the development of the flag. The earliest, the Grand Union flag of 1775, incorporated the British Union Jack within 13 stripes. Stars first appeared in 1777, but there was no official arrangement for them. Betsy Ross arranged them in a circle, while the Bennington flag, used in the Battle of Bennington, had stars in a horseshoe arrangement around the number "76." The Flag Act of 1795 created a flag with 15 stripes and 15 stars, but in 1818 Congress reduced the number of stripes to 13 and specified that a star be added for every new state admitted to the Union. The flag-before-last had 49 stars; it flew for only one year, from July 4, 1959, when Alaska was admitted to the Union, until July 4, 1960, when Hawaii made it an even 50 stars.

Free tours of the FBI are given weekdays from 9 to 4:15.

Just across Ninth Street lies Market Square, a triangular open space that was once the site of Kann's Department Store. A Navy Memorial and a performing center for military bands will rise here sometime next year. The memorial and the surrounding park are being planned to retain the view up Eighth Street to the National Portrait Gallery. At the Seventh Street end of the square, near the Archives Metro station, is a bronze equestrian statue of Gen. Winfield Scott Hancock, a hero of the Mexican War and the Civil War. Hancock might have been riding up the avenue rather than sitting on the sidelines had it not been for a mere 10,000 votes. That was the margin by which Democrat Hancock lost to James Garfield in 1880.

Take a short detour off the avenue to stroll up Seventh Street, downtown Washington's art center. Browse through a dozen private galleries. Eat and/or catch an art show or a stage show at D.C. Space, an artists' restaurant, and check the progress of Gallery Row, a Pennsylvania Avenue Development Corporation project at the corner of Seventh and D streets NW. The project will reconstruct a 19th-century commercial building and turn it into gallery space, shops and restaurants.

At the corner of Seventh Street and Indiana Avenue, take a short jog to the left and browse through the Artifactory at 641 Indiana Avenue (brass goddesses from India, Chinese wall hangings, African woodcarvings, mosque lamps from the Middle East) and Litwin's at 637 Indiana Avenue (antiques and used furniture). The shop, which has been in the Litwin family since 1912, has three stories. You'll have to climb the stairs, but the furniture rides from floor to floor in what may be world's oldest operating elevator. An Otis, it was installed in the 1850s just after Elisha Graves Otis' safety elevator at the Crystal Palace Exposition in New York and is almost identical to the plans Otis filed with the Patent Office. It isn't automatic; it works with ropes and counterweights. Store owner Fred Litwin says it works perfectly and has never needed major repair work. WHATEVER HAPPENED TO THE APEX LIQUOR STORE AND THE TEMPERANCE FOUNTAIN THAT DRIED UP?

From the early '40s to the early '80s, the Apex Liquor Store on the corner of Pennsylvania Avenue and Seventh Street NW was a major attraction for tourists and locals, who never tired of chuckling over the ironic positioning of the Temperance Fountain right in front of the store. Actually, the fountain was there more than 80 years before the liquor store opened. The fountain was one of many across the country erected by a San Francisco dentist and teetotaler named Henry Cogswell. Cogswell reasoned that if people had clean, cold water to drink, they'd pass up the intoxicating stuff. The water poured out of the mouths of two entwined dolphins, the overflow filling a trough for horses. First, the city covered over the trough, then stopped stopped providing ice for the fountain's cooling device, and finally turned off the water. But Cogswell had his revenge in a sense, because the flow of liquor from the Apex has stopped, too. The refurbished building is now Sears House, housing Sears World Trade, a Sears Financial Center headquarters and Sears' government affairs offices. Sears House incorporates the liquor store building at 633 Pennsylvania Avenue, originally the St. Marc Hotel in the 1850s, and two buildings next door, which housed Gilman's Drug Store and the studio of photographer Matthew Brady. It was there that Brady took the photographs of Lincoln that served as the images on the $5 bill, the Lincoln penny and the three-cent stamp. Sears House isn't open to the public, unless you want to come in and talk about a financial plan or buy some insurance.

As you cross to the south side of the avenue, imagine you're entering the vast, covered Central Market that occupied the south side of Pennsylvania Avenue from the early 1800s until it was demolished to make way for the National Archives building in 1931.The Archives has two entrances. The door on Constitution Avenue leads to the popular exhibits, such as the Constitution, the Declaration of Independence and the current multimedia show on Recent America, which includes a film clip of an actor named Ronald Reagan training Army recruits. The door on Pennsylvania Avenue is for people who want to trace their roots. A 12-minute slide show, shown weekdays and Saturdays 9 to 5, will help get you started searching through the vast array of records. Tours of the Archives are given weekdays by advance reservation. Call 523-3184.

In the small park in front of the Archives sits a desk-size, desk-shaped memorial to FDR. He reportedly once told Justice Brandeis that he wanted no memorial bigger than his desk. This one reads simply In memory of Franklin Delano Roosevelt, 1882-1945.

If you ever arrange to meet someone at the Apex Building, make sure you specify which one. In addition to the aforementioned Apex Liquor Store building, there's the Apex Building that houses the Federal Trade Commission. It sits at the apex of the Federal Triangle, where Pennsylvania Avenue meets Constitution Avenue between Sixth and Seventh streets. The statues at the Sixth Street end of the building show a muscled man subduing a spirited horse, a metaphor on government controlling the free enterprise system. Also interesting are the aluminum panels on the doors, showing ships and airplanes, the old and new vessels for conducting trade.

A large overflowing fountain honoring Andrew Mellon fills the triangular part that's the real apex of the Federal TrianBFgle. It sits across Constitution Avenue from the West Building of the National Gallery, which Mellon endowed with his mony and his art collection. If you enter the gallery through the Constitution Avenue entrance and make your way through seven centuries of western art, then wander through the cafeteria and past the waterfall, you'll be in the East Building, which actually does border on Pennsylvania Avenue. The new building, by I.M. Pei, features changing exhibits, but some things are always there: the exhibit of small French paintings from the Ailsa Mellon Bruce Collection, the hanging tapestries by Joan Miro and the tower plastered with cutouts by Henri Matisse.

The other side of Pennsylvania Avenue was the site of a less pretty scene. In 1932, the ragtag "Bonus Army" came to Washington to get bonus money they thought was coming to them for their participation in the Great War. They took up residence in some vacant buildings in the 500 block of Pennsylvania and were routed, on July 28, 1932, by U.S. Army troops. Walt Whitman also lived in this block, in 1864, and earlier it housed one of the city's popular gambling palaces. All these buildings were eventually demolished, and the block is now occupied by the D.C. Unemployment Office.

Check out the progress of the new Canadian chancery in the next block. It's scheduled to be completed in 1986 on Pennsylvania Avenue next to John Marshall Park, an oasis that opened last year. The park has benches scattered in a studied- casual way to make them look like the chairs in the Tuileries, although actually they're set in concrete. Sit a while, then climb the terraced steps, checking the time on the sundial from John Marshall's garden in Richmond. The two men in three-piece suits sitting on the garden wall and playing chess aren't real, but wonderfully lifelike bronzes by Lloyd Lillie. There's also a delightful fountain by David Phillips with bronze lily pads, frogs and dragonflies. A plaque by the fountain reads: "Near this spot on the north side of C Street was a city spring from which in 1808 water was first piped through the streets of Washington." The vista up the steps is a sweeping one of the Pension Building roof and the original city hall, built in 1820 by English architect George Hadfield and now used as one of the courthouse buildings.

In front of the park, presiding over the traffic, is an allegorical statue of Major General George Gordon Meade, who commanded the Union forces at Gettysburg. The statue, donated by the state of Pennsylvania, has Meade in uniform surrounded by partially draped men and women.

From Meade Plaza, it's a clear shot to the Capitol, with only the Capitol Reflecting Pool and the Grant Memorial in between. Grant may not be an ideal subject for the president- elect to dwell on just before he arrives at the inaugural site. After a presidency marked by two terms of corruption and scandal, Grant lost all his money through bad business investments. A hero to the last, he struggled, while dying of cancer, to finish his memoirs and provide some income for his family.

So, many things have changed for the better, after all. Today, presidents get big pensions. And getting there -- at least the trip down Pennsylvania Avenue -- is a lot more fun than it used to be.