THE WEATHER outside may be frightful, but deep in the womb of the earth it's warm and delightful. And if you play your cards right -- your Metro fare cards -- you can stay cozy all day. And you don't have to ride forever like Charlie on the MTA. The Metro maze had places where you can eat, watch Chinese flicks, have your picture taken, shop for an armoire, drink, watch a baker, see the Wright brothers take off, work a computer, learn about the Washington that was, use a rest room, eat, trade baseball cards, read vintage comic books, admire architecture, and eat -- without ever breathing any of the cold, cruel air outside. First, of course, you have to bundle up and get yourself to the nearest Metro stop. As the wind whips you down the escalator, start unbuttoning your down jacket. Buy a Farecard for about $4 worth of rides and then relax. Here are some of the ways to while away a long cold Saturday underground:

From anywhere in the system, 50 cents will take you to L'ENFANT PLAZA: Take the long escalator up, brave the draft at the top, then enter the underground shopping center. Have a pina colada (non-alcoholic) and a Panda Banana at Danny-Yo. It's not Dominiue's so they don't use real panda, just a banana topped with frozen banana yogurt (to remind you of how cold it is outside), honey and grated coconut.

Browse through the Velvet Pumpkin, an unusual store featuring exotic soaps, loofahs and antique armoires the owner found in Europe ($600 and up). The store gets its unusual name from a statement of Thoreau that he'd rather "sit alone on a pumpkin and have it all to myself than be crowded on a velvet cushion."

Take in a Chinese-language double-feature at the American Theatre. Call 554-2111 to find out what's playing.

Warm up with a bowl of chili, with rolls, butter and coleslaw at the People's Drug Store for $1.25. Then think about the poor folks out in the cold as you down a jumbo chocolate sundae for 49 cents.

Stroll into the Peddlars Two and listen to some hot rock.

Take the elevator upstairs to the hotel. Pretend you're waiting for someone as you curl up in one of the plush velvet chairs in the lobby and read the morning paper. Or sink into the couch next to the lobby bar and sip a and read the morning paper. Or sink into the couch next to the lobby bar and sip a Courvoisier. Gaze outside at the fountain: It may freeze right before your eyes.

Wander into the Greenhouse restaurant for lunch and linger so long it's time for afternoon tea at the Apple of Eve next door. Admire the bronze statue of Eve by Harold Caster and see if it still has a wad of gum stuck in its navel.

Go back downstairs and put a dollar in a machine called the Face Place, which takes a color Polaroid picture ofyou. Then go deeper underground, put your Farecard back in the turnstile and ride three stops to -- METRO CENTER: Indoor activity here is all at Woodies. There are several restrooms, and, of course, things to buy. For a warm feeling, look at the spring clothes, try on bikinis, and spray yourself with flowery perfume. Another 50 cents marked off your Farecard and you take a three-minute ride on the Red Line to -- FARRAGUT NORTH: You'll be out in the cold unless you take the L Street exit. Not the one that's closed on weekends, but the exit at the very end of the platform. Then you'll find yourself in the Connecticut Connection, where you can watch a baker at work shaping croissants (mornings only), buy some magazines, use the restroom and eat, eat, eat.

If it's before 11 a.m., try the Mighty Mex breakfast at Taco Ole: scrambled eggs wrapped in a buttered tortilla topped with chili sauce, tomato, Canadian bacon, refried beans and cheese. Or if you're watching your weight, have a bagel with cream cheese and chives, washed down by a glass of grapefruit juice from What's In The Oven? Stick around for lunch -- fried chicken and potatoes from Western Chicken and Chips, a jumbo frankfurter from Top Dog, or something healthful such as spinach salad from Radishes and Rainbows. For dessert, a chocolate-chip cookie from the Cookie Connection or a giant chocolate lollipop from Chez Chocolate. The best part of the Connecticut Connection is that not everybody in your party has to choose food from the same establishment. You can go your separate ways, then meet at a table in the middle. While you eat, forget about winter and gaze at Les Fleurs D'Angelo -- hothouse gladioli behind glass. Then, making sure you've finished all your food 'cause there's no eating allowed on the Metro, trade another 50 cents off your Farecard for a ride on a Red Line train marked Silver Spring. Get off at the fourth stop and you'll be at -- UNION STATION: Don't take the exit marked Visitors Center, or You'll be out in the cold for at least half a minute. Instead, follow the signs leading to the train station. Pretend you're waiting for a train to Florida and warm your insides with something strong in the Observation Car as you watch the trains warm up and load up. As you sip, you may decide to take the ultimate underground getaway by buying an excursion ticket to New York for $40.50 round trip. Once in the Big Apple, you don't have to breathe its even colder air. Take the subway -- even though it's not as nice as ours -- from Penn Station to Lincoln Center and go upstairs for a matinee of the Metropolitan Opera (if you've left Washington on the 9:05 train, that is). This Saturday for a mere $3 you can stand through a heartwarming performance of Fidelio. Then subway it back to Grand Central Station and eat a few dozen oysters in the Grand Central Oyster Bar before making your way back through the underground to Penn Station and Washington. Depending on how many beers you've consumed with your oysters, this optional, all-day side trip won't have cost you more than $50.

If you decide against the side trip, just climb the ramp and stroll around the Visitors Center, which used to be Union Station. The Station, which architectural historian Diane Maddex called "a star in Washington's galaxy of truly heroically proportioned interior spaces," was alegedly modeled on the Baths of Diocetian in Rome. It was built in 1903 as an incentive to get the railroads to move their tracks off the Mall and tear down the old station, where the National Gallery now stands. Beginning in February, the National Park Service will lead walking tours through the center and detail the history of the station everyday at 11.

Look at old photos showing "Two Centuries of Change -- the Idea of Downtown Washington" in an exhibit assembled by the City Museum Project, Inc., a group trying to start a city museum. One photo shows people riding horses down Pennsylvania Avenue in 1871 to celebrate the fact that the street had just been paved with wood blocks.

Examine the Kachina dolls, the Indian pottery and jewelry, and the Navajo rugs in the Department of Interior shop.

Try the touch computer.By pressing your finger in the right spot you get a screenful of information about Congress, sightseeing tours, and where to stay, and it's fun to work even if you don't want any of this information.

Thumb through the restaurant guide, which consists of actual menus of Washington restaurants, arranged by cuisine type.

Browse through the bookstore, then walk through the doors that used to lead to the trains and now lead to the gallery, which gives a year-by-year photographic history of the U.S. from 1776 to 1976. You learn, for example, that in 1940 the U.S. population was 132 million; FDR was reelected for the third time, and the first peacetime draft ceremony was held in Washington.

In February, there will be series of events and exhibits marking black history month. Call 523-5300 for the events of the day you plan to visit.

Have a chat with one of the street people who gather in the center on cold days. Then filter back down, through the station, to Metro. Spend another 50 cents and let the Red Line whiz you back to Metro Center, walk downstairs to the Blue Line and go under the river to -- THE PENTAGON: There's no action here on Saturdays, so save your 50 cents and don't go out. But if you stop by any weekday you can take a free tour of the Pentagon. Just take the escalator from Metro and walk to the north end of the concourse -- all underground. Tours leave every 30 minutes from 9 to 3:30. The pastry shop under the Pentagon is also worth a visit. Then hop back on the Blue Line and ride two stops to -- CRYSTAL CITY: First follow the signs through a yellow brick maze to Crystal Plaza and take an elevator to the main lobby of Crystal Plaza 3 to see the National Inventors Hall of Fame, part of the U.S. Patent Office. From the exhibits there, you'll learn that Carl Djerassi, who was inducted into the Hall Of Fame in 1978, holds patent 32,744,122 -- for oral contraceptives. Press a button and you'll start a film strip about "Al" Edison. Push another button and the wright brothers step out of a model of the sheds at Kittyhawk and onto the sand. Slowly, almost imperceptibly the plane rises a few feet -- on the model only a fraction of an inch -- off the beach. Special exhibits are scheduled for National Inventor's Days -- February 9 and 10.

Take the elevator back down to below ground level and follow the signs to the Crystal Underground, a replica of a turn of the century village where people shopped on streets rather than in shopping malls. It's like a Hollywood set, but very well done with a rainbow of clapboard storefronts with stained glass windows and lots of places to stop and rest.

In antique alley, browse among the quill pens in the calligraphy shop and blow a penny on a baseball card at Gerhard's World of Baseball. Or bid for rarer cards in the silent auction on the bulletin board.

Haggle for an old Muskie button at the Ancient Coins stand, which also sells beer cans.

See how long you can read the old comics in the Comic Book and Science Fiction Shop without being embarrased into buying one. Then leaf through the stack of movie lobby cards and buy the one from "The George Raft Story."

Press you nose against the glass of the lobster tank in Larimer's, and plan a whole new look for you lavatory at the Bed and Bath Shop. Then draft into Phase III, a gazebo-like structure housing multiple food and drink places. Try the pizza at Little Italy. For geographic distribution, get a slice of Black Forest Cake from Happy Endings and wash it all down with a Perrier-with-a-twist from the Waterworks.

Eight hours and $3 worth of Farecard later, you'll finally have to face the weather again, at your home-port Metro station. As you emerge from the womb, with wind and snow whipping your face, take heart -- and start planning your next underground Saturday.