TO APPRECIATE the Lexington Market, you first have to come to terms with what it isn't. It isn't Disney World. There are few amusements except for the pleasures of buying and eating (or taking home) good food. It is not brand new. It is not beautiful, in any ordinary sense of that term. And it is not so fanatically manicured that you can eat off the floor. (You might get a mouthful of sawdust if you tried.)

So what is it? The Lexington Market is simply a vast array of 160 stalls in two immense buildings in downtown Baltimore. Subsidized by the city, it's the oldest continuously operating municipal market in the U.S., renting stalls to small food merchants--butchers, greengrocers, bakers, dairymen, and, in keeping with the times, purveyors of such items as pizza and gyros.

It all started in 1782, when John Eager Howard donated some pasture land to establish a market and meeting place where farmers could take their goods and where the public could go and buy them. A succession of sheds was later built as the market grew. In its heyday in the mid-19th century, 600 farm wagons were serving crowds of 50,000 people on paydays, and by 1925 there were a thousand stalls under three city blocks of sheds.

Then in 1949 a six-alarm fire razed the market. The phoenix that rose from those ashes--the present East and West Market buildings--is today's Lexington Market, with the addition last year of a new, zippy-looking arcade with additional stalls. Relatively zippy-looking, that is, because there's been a conscious decision on the part of the planners to retain--even to nurture--the market's old image.

"We're definitely not the new Harbor Place, or an immense fast-food palace," says David Imre, the market's director of advertising and promotion. "We're not looking for McDonald's or Pizza Hut. We're trying to take this market back to its roots, to rent the stalls to individual merchants. We had around 500 proposals for 22 new stalls in the arcade. So we could pick and choose. And we mainly chose independents. There were three applications for just one pizza stall. We gave it to a couple of brothers, 19 and 22 years old. They're enterprising, they had the capital, and they bake good pizza."

It's a nice gesture, trying to bring back the old days. But what were the old days? Why did a horde of 50,000 people show up at the Lexington Market on payday a hundred years ago?

Before refrigeration, supermarkets and shopping centers, markets served as a societal magnet, a place where people could buy all their food under one roof and, just as important, meet people they knew, to engage in a social ritual that defined their ties to the community.

There are merchants at the Lexington Market who can recall the tail end of the good old days when the market was still a flourishing center of commerce in downtown Baltimore. John Liberto, born four blocks away, has worked his produce stand, boy and man, for the past 52 years. He and his brother, Joe, took over from their father, a Sicilian immigrant who opened it in 1890 after years of pushing a produce cart on the streets of the city.

"Back in the '30s we had customers come in limousines, with chauffeurs." Thinking back, John Liberto warms up to the subject. "People knew how to pick produce then, they knew how to tell a ripe melon. Today, the young people, they don't know the difference."

His family's ties to the market will be broken when he and his brother, who is childless, retire. "My son has a good job with the phone company. He doesn't want to get up at three in the morning in the produce business. Why should he?" says John Liberto.

At Foell's Meats, in the market since 1900, the family connection will continue. When 70-year-old Eddie Foell and his 80-year-old brother Charlie retire, Eddie's son Tom will take over.

"Years ago," Eddie recalls, "people lived close by and they'd come on the streetcar to shop." He puts aside the platter of ox tails on which he's been working. "In those days we had a lot of specialization. The market had pork stalls, beef stalls, poultry stalls, veal and lamb stalls."

As far as practical, the present managers of the Lexington Market want specialization to continue.

"We specify in the lease what each stand can sell," says Imre. "We don't want to end up with dozens of miniature Safeways out there. For example, one of our merchants can do just smoked pork. That's his special item, the thing that made his name."

Granted that the market once played a major role in the life of the city, is there really a function left for it in the '80's? Imre thinks so: "One of the things we offer is special service. At our meat stands, you can talk to a real butcher, not just a supermarket meat cutter. You can get advice. You can get special preparation."

Harry Schafer (who has been in the market since 1945) of Schafer's Meats (which has been there since at least 1874), agrees: "Absolutely. I create special cuts, like mock duck out of a lamb shoulder. And my crown roast is done correctly, not just hacked up and wrapped around."

Eddie Foell echoes that: "Tell me how many guests you're going to have and what you want to serve. I'll tell you how much you need, fix it up for you, and advise you on how to prepare it."

Imre says competition from the new supermarkets that have personalized butcher and seafood services is going "to help us, not hurt. There's a whole generation of shoppers under 40 who've never really talked to a butcher or a fish man, who don't even realize you can get that kind of service. When they experience it for the first time in a supermarket, when they realize what they've been missing, they're going to like this place even more."

Harbor Place is a 15-minute walk from the market. Imre thinks the two attractions are so dissimilar that they aren't in competition: "Harbor Place is great for out-of-towners, but for a lot of people who live here it's already getting old. How often do you really want to go back to see it? Lexington Market is more for the natives, for repeat customers, for regular shopping trips. People come here the first time just to see the place, but they come back to shop."

Of course the line of demarcation between tourist and shopper is never that clear, and the people at the market know it. For the out-of-town conventioneer, Faidley's Seafoods has handy Styrofoam-lined carrying cartons, ready to go. Stow your softshell crabs under your airplane seat and tonight you'll be enjoying them at home in Dubuque.

Imre's optimism and Faidley's cartons notwithstanding, the market has fallen on relatively hard times in recent years. First there was the decline of the affluent downtown neighborhoods that once brought the market a steady supply of customers. Then, over the past decade, subway construction and urban renewal choked traffic near the market and made parking a nightmare.

But signs of a turnaround are in the air. A new Lexington Market subway stop is nearing completion, and coming are a new face on the buildings, a parking garage and a pedestrian walkway on the Eutaw Street side.

"The subway may bring people here like the old street car did," reflects septuagenarian Eddie Foell. Downtown office workers are another potentially large source of customers. There are about 6,000 at the state office building, which will be just a subway stop away. Imre gets excited just thinking about them.

"It's a matter of changing people's food shopping habits," he says. "Today, the working homemaker leaves a downtown office around 4:30 or 5:00. An hour or so later, she's fighting the longest lines of the day in her neighborhood supermarket. What I'm looking forward to is a change in that pattern. A person could hop on the subway at lunch time, rain or shine, be here in a few minutes, have some lunch at one of our stalls, buy something special for dinner that night, and stow it in the office refrigerator until it's time to leave."

Will history bear out David Imre's optimism? Will Eddie Foell's son take over a revitialized meat business? Will the young brothers become the pizza barons of Baltimore? Will the Lexington Market once again be a major commericial center in the city of Baltimore?

In the meantime, the market is a nifty place to visit, and the trip from Washington is simple, but bear in mind that although the market is open Monday through Saturday from 8:30 a.m. to 6 p.m., many of the stalls are traditionally closed on Mondays. Take I-95 to Baltimore, exiting at Russell Street, which becomes Paca Street and leads directly to the market. Indoor parking is adjacent.

Stop first at the market office on the second floor of the East Market building for a map (also available at the Ben-Lux tobacco shop in the arcade) of the complex, then explore. Hint: you don't have to eat on your feet. There's a pleasant area on the second floor of the arcade with tables and chairs.

Try the raw bar at Faidley's Seafood, which has been in the market since 1887 and claims to serve over a million clams and oysters a year. And look particularly for the marvelous backfin crabcakes, with big flakes of crabmeat unsullied by filler or excess mayonaise.

The steak subs at Andy's Best may be the best bargain in the market, or in all of Baltimore, for that matter. Two dollars buy a gargantuan pile of grill-fried eye round and onions mounded on a sub roll with lettuce, tomato and oregano--and french fries, besides.

For a wonderful shrimp salad, the kind that's crammed with whole shrimp, have a sandwich at The Crab Pot-- 1/3 pound or so on a good kaiser roll for $3.25.

You'll find the young Caltabiano brothers, Carmin and Nello, plying their pizza trade at the Italian Stallion stand in the arcade. Although their pizza might not win a gold medal in Manhattan (or on Long Island, even,) it's very good--the genuine New York-style article, and definitely worth a try.

If you're in the mood for something lighter, look for Irene's, where you can get a pint of a beautiful fresh salad for $1.50.

But, if there's one stop at the Lexington Market that would make the whole trip worthwhile by itself, it's the Castle Farm Dairy. The farm, near Emmitsburg, Md., has had a stall in the market since 1882. Sample some of their products and you may never again want to use the dairy case at your supermarket. Try the homemade cream cheese, which isn't made with gum, actually has the flavor of cheese and won't cement your jaws together. Put some in your bagel and realize what you've been missing. Had homemade root beer lately, deep flavored with sassafrass and yeast? Another eye-opener. And how about homemade yogurt, smooth and gentle? Or local grape juice, with a flavor the bottled version can't match? Ice cream buffs, be prepared for a 21 percent-fat marvel that beats the trendy stuff they sell in Georgetown, and at about half the price. Seasonal flavors--raspberry and peach in summer, apple-cinnamon in October. Have an ice chest in your car, to take things home.

On your way to the car, stop outside the East Market building on the Eutaw Street side for a bag of Konstant's peanuts, roasted in the shell as you watch. They could probably be stored until your next visit to the circus or ball park and still be fresher than the hawkers' offerings.

Here are some recipes from the people who operate the stalls at the Lexington Market. NANCY DEVINE'S BACKFIN CRABCAKES (Faidley's Seafoods) (Makes 4 to 6 crabcakes)

These are the ones served at Faidley's. Nancy Devine (nee Faidley) described the recipe to us as she waited on a line of customers. She never lost a beat. 1 pound backfin crab meat 1 cup crushed Saltines 1 cup mayonnaise 1 tablespoon dijon mustard 1 tablespoon worcestershire sauce 1 teaspoon Old Bay seasoning 2 eggs

Spread the crab in a shallow pan. Add the crushed saltines and toss lightly. Be careful not to break up the crabmeat pieces or pulverize the crackers. (Over-crushing yields a mealy crab cake.) Mix the remaining ingredients and mix this batter with the crab and crackers just enough so you can form cakes. The art is in the handling: firm but light. Refrigerate for at least 30 minutes, or overnight if convenient. When ready to serve, fry quickly in hot oil. Brown one side, turn, and brown the other, then quickly remove. The cakes should be just heated through. RED SOISTMAN'S SAUTEED CRAB MEAT WITH SMITHFIELD HAM (Soistman Bros. Meats) (4 servings) 1/4 pound butter 1 pound backfin crab meat with shell membranes removed 1/4 pound chopped Smithfield ham 1/4 teaspoon ground thyme 1/4 teaspoon ground sage 1/4 teaspoon red pepper 2 tablespoons chopped fresh parsley 1 tablespoon chopped chives or scallion greens 1/4 teaspoon garlic powder

Toast points for serving

Melt butter and add remaining ingredients. Over moderate flame, stir until heated only. Serve on toast points. MRS. J. LEONARD LENTZ' STEAKS STUFFED WITH OYSTERS (J. Leonard Lentz Meats) (4 servings) 4 beef tenderloin steaks, cut 2 inches thick 8 oysters, shucked 1/4 teaspoon salt Fresh ground black pepper 4 tablespoons butter, melted (optional) 1 tablespoon finely chopped fresh parsely (optional)

Have a butcher cut a pocket in each of the steaks. Sprinkle the oysters with the salt and a few grindings of pepper, then put 2 oysters into each steak. Close the pocket with small skewers. Pat the steaks dry with paper towels and sprinkle fresh pepper over them.

Over hot coals on the barbecue grill, brown them quickly for 1 to 2 minutes. Turn with tongs, and grill for about 8 minutes turning several times.

Just before serving, pour the melted butter combined with the chopped parsley over the steaks. RED SOISTMAN'S SAUERKRAUT WITH APPLES (Soistman Bros. Meats) (6 servings) For spice bag: 1/2 teaspoon caraway seeds 8 juniper berries, crushed 3 bay leaves For the sauerkraut: 1 tablespoon lard 1 cup diced onions 2 pounds sauerkraut washed with cold water and squeezed dry 1 1/2 teaspoons sugar 2 cups cold water 4-pound piece smoked ham (smoked butt or smoked loin) 1 cup peeled and cored diced apples 1 large peeled potato

In a spice bag or cheese cloth, tie together the caraway seeds, the juniper berries and the bay leaves.

In a 4-quart casserole, melt lard and brown onions. Add sauerkraut, sugar, and water. Mix together to loosen sauerkraut. Bury spice bag in center of kraut and place meat on top of kraut. Bring to boil. Simmer covered for 20 minutes. Add apples. Remove the spice bag, grate potato into sauerkraut, and discard bag. Cover and simmer for 2 hours. LA RUE E. SCHAFER'S KENTUCKY BUTTER CAKE (Harry J. Schafer's Sons Meats) For the cake: Butter and flour for pan 3 cups flour 2 cups sugar 1 teaspoon salt 1 teaspoon baking powder 1/2 teaspoon soda 1 cup buttermilk 1 cup butter, softened 2 teaspoons vanilla or rum extract 4 eggs For the butter sauce: 3/4 cup sugar 1/3 cup butter 3 tablespoons water 1 or 2 teaspoons vanilla or rum extract

Generously grease and lightly flour a 10-inch tube pan. Lightly spoon flour into measuring cup; level off. In large bowl blend all the cake ingredients at low speed until moistened. Beat 3 minutes at medium speed. Pour batter into prepared pan. Bake at 325 degrees for 55 to 70 minutes or until toothpick inserted in center comes out clean.

In small saucepan, combine sauce ingredients. Heat until butter melts. Do not boil. Pierce hot cake 10 to 12 times with long-tined fork. Slowly pour hot sauce over cake. Cool upright in pan 30 minutes. Remove from pan. RED SOISTMAN'S SAUTEED CHICKEN AND SQUASH (Soistman Bros Meats) (4 servings) 4 chicken legs 4 chicken thighs 1/4 cup olive oil 1 pint squeezed tomatoes with 1/2 teaspoon sugar Salt and pepper 1 bay leaf 6 large garlic cloves, minced 2 large onions, cut in 8 pieces each 2 ounces Smithfield ham, shredded 1 large squash, cut in bite-sized pieces (summer, bush, zucchini or eggplant) 1 beaten egg 2 tablespoons chopped parsley

Wash and dry chicken pieces. In a Dutch oven brown pieces lightly in olive oil. Remove chicken to platter.

Add tomatoes to 2-quart saucepan with salt and pepper and bay leaf. Cook until liquid has evaporated.

To olive oil now add minced garlic, onions and ham. Saute' for 5 to 8 minutes. Add tomato sauce and chicken, cover and simmer at moderate heat for 20 minutes. Add squash, cook 15 minutes. Remove chicken to serving dish.

To 4 to 6 tablespoons of tomato sauce, stir in egg and return to pot for 2 minutes. Do not allow to boil. Pour sauce over chicken. Garnish with parsley.

The final touch, according to Soistman: "Have plenty French or Italian bread available to sop up juices."