TWO FRIENDS are leaving the country. One is headed for Mexico, the other for a Peace Corps tour of Africa, so an exotic experience is called for. The French-accented voice at Marrakesh, a Moroccan restaurant and the culinary counterpart of the Greatest Show on Earth, promises a long, sumptuous evening.

Entering Marrakesh is like arriving at Oz: The blank facade is marked only by cryptic Arabic script, and after our resonating knock on the enormous, slightly forbidding door, the hostess peers out and beckons us inside.

We are easily assimilated as we sink into low sofas and velvety embroidered pillows around an engraved brass table. Act One begins as a kneeling waiter pours warm water over our hands, held over a great brass basin. It's the first of three handwashings, because we'll be eating with our hands. It's more fun than it sounds, as long as everyone cooperates. Drinks are ordered from a long list, and the adventurous try arak, a light but potent anise-flavored beverage from Lebanon.

Then begins the leisurely procession of eight aromatic courses, redolent of sugar and cinammon, chicken and lamb and spices, during which we meet members of neighboring parties, perhaps a course behind us, who crane over to ask, "What's that?"

Intermission: the lights go out, waiters whiz by bearing sparkler-spangled cakes, and the whole restaurant sings a Moroccan-tinged "Happy Birthday" song. Then a ching! of finger-cymbals heralds the entrance of belly-dancer Shari for several numbers. She's actually a data processor during the daylight hours, but you'd never guess it by the truly impressive isolation of her body parts. Later the staff initiates a jolly snake dance through the long room, seeking out agreeably arak-plied diners for a little exercise between courses.

It's all wrapped up in a big finish -- another hand-washing, then fresh fruit and mint tea, poured into glasses from a daring height.

Marrakesh can comfortably accommodate groups of two to 22, and the unhurried, attentive service plus the sheer closeness and coziness can lead to the sharing of secrets and sentimental stories, with more than a few laughs.

MARRAKESH -- 617 New York Avenue NW. Open Monday to Friday, 6 to 11 p.m.; Saturday, 5 to 11; Sunday, 5:30 to 11. Reservations are required and dinner is prix fixe $18, but drinks are not included, so dinner for four can easily climb to a worth-it, but surprising nonetheless, $150 and higher. Marrakesh doesn't accept credit cards, but personal checks are welcomed.Call 393-9393.