We are a mile from our hotel in Sanaa, North Yemen, when the hired driver swings down a narrow lane, parts a sea of squawking chickens and skids to a halt. Ducking inside a stone hut, he emerges brandishing a curved, nine-inch stainless steel dagger.

"Just in case anyone bothers us on the way," he says, thrusting the knife into an elaborate scabard. The driver, whose name is Ali, explains apologetically that he removed the blade before visiting a friend at the hospital, where weapons are forbidden. Almost everywhere else, Yemenis wear the jambiya the way other men wear trousers.

Ali passes through two military checkpoints and winds into the mountains surrounding the Yemeni capital. The road ends at a tangle of earthen towers tucked in a mountain crag. At the hotel in Sanaa, Ali insists that this village, called Shibam, was the "one place that must be visited" on a day trip from the capital. At the Shibam street market, we discover why.

"The best qat in Yemen grows near here," Ali says, parking beside a stall where a dozen men are haggling over what looks like a pile of yard clippings. Ali elbows his way through the crowd and returns with an armful of green leaves, wrapped in cellophane. He stuffs a few in his cheek, sucks for a moment and smiles.

"We call it Yemen salad," he says, teeth already green with the shrub. "Qat is very good for the head. You have ideas all over the world."

Mission accomplished, Ali sets off down a side street to show his companions an ancient mosque.

Jambiyas and qat are the yin and yang of Yemeni society. Weapons and weed, menace and mellowness.

From the waist down, the men of North Yemen are fierce mountain tribesmen: sandals, skirt and a gaudy dagger that runs from the bellybutton to the middle thigh. In remote areas, where tribal law prevails, peasants often add a pistol to their waistline armory.

From the belt up, Yemeni males look more like Bowery bums. Rumpled polyester shirts protrude from rumpled sports jackets. A rag is tied loosely around the head, accompanied, most of the time, by a mouthful of qat and an amiable, slightly glazed expression. In the afternoons, when almost every adult male has an apple-sized "chew" in his cheek, Yemen looks like a nation of third-base coaches on a last-place team in mid-September.

"I ended up getting great pleasure from its gentle stimulation and the vivid dreams which followed," reported Paul Botta, a 19th-century French traveler, who found qat "slightly intoxicating."

Even when not under the influence, Yemeni speak vividly of their country's history. Yemen's fertile land and strategic location, at the base of the Arabian peninsula, made it a prosperous crossroads in biblical times.

It was here that the Queen of Sheba loaded camels with gold and spice and frankincense for the journey to King Solomon's court. For centuries after, Yemen controlled the rich trade routes from Africa and the Orient, prompting Romans to call the region Arabia Felix, which means "happy" or "fortunate" Arabia.

After the Turkish conquest in the 16th century, though, Yemen entered a period of semi-feudal isolation from which it is just now emerging. The Turks and British divided Yemen into north and south in 1904, and the two neighbors have fought several wars. Today, South Yemen is a Marxist-ruled state, almost completely closed to foreigners. North Yemen's nonaligned military-led government is gradually opening its country of 9 million to oil companies and tourists.

Nevertheless, North Yemen remains a challenging tourist destination. During a two-week driving tour of the entire country, I found few modern amenities outside the major cities, and little spoken English. The terrain is a rugged patchwork of desert and mountains, crisscrossed by two-lane roads that are guarded by heavily armed soldiers and tribesmen. Yemen isn't threatening to Westerners, but it is an underdeveloped land deserving of caution.

The reward is a glimpse of a traditional Arab culture that has changed little for centuries. Yemen is roughly the size of Nebraska and is divided into three distinct regions. The eastern desert is Bedouin in character, with camel riders roaming sand dunes spooned out by the wind. It is here, in Marib, that the Queen of Sheba built a temple to the moon god: eight stone columns rising from the edge of the vast Arabian desert called the Empty Quarter.

In the central highlands, mud fortresses perch improbably atop sawtooth crags, keeping watch over fields that once produced the finest coffee in the world, named for the Yemeni port of Mocha. Here, peasants nudge water buffalo and wooden plows across terrace farms that climb, in broad green stairs, up the face of 10,000-foot mountains.

The third region is a flat coastal plain, where the Arab world meets the African. In villages of grass-roofed huts, black women with nose rings and neck rings lead camels while balancing baskets on their heads.

One morning in the village of Rayda, an Arab boy grabbed my hand and insisted in broken English that he would show me around. He led me through the street market, or souk, and then down a dusty lane to two stone houses at the edge of town.

"These are our Yahood," he said, introducing me to two shoemakers named Ezra and Abraham. I had read that there were still Jewish artisans in Yemen, descended from Jews who fled there in the 1st century A.D. But apart from tight ringlets of hair, drooping down beside their ears, these dark-skinned, Arabic-speaking men in shifts and sandals were indistinguishable from their Moslem neighbors.

Nor did I fit their image of a Jew, despite my repeated statements that this was so.

"Mish mumkin," Ezra said in Arabic. Not possible. The two men stared at my light skin and Western clothes and laughed.

I asked if they had a Torah, and Abraham brought a tattered prayer book from inside. When I read a few lines in Hebrew, children and women, some of them veiled, were called out of the house to bear witness. I felt as if I were being bar mitzvahed a second time.

"Mumkin," Ezra finally declared, spitting qat juice in the dust. It is possible. He scribbled his name in Hebrew and invited me to celebrate the Sabbath next time I happened to be passing through Rayda.

If the Yemeni countryside appears at turns medieval, even biblical, its capital city of Sanaa seems lifted from a fairy tale or a Coleridge opium dream.

The old city, that is. Sanaa, like many Arab cities, is really two communities. The modern capital, swollen with rural migrants over the past 20 years, now sprawls across a sweeping mountain plateau; it is a congested and often ugly mess of gridlocked traffic and concrete houses, inhabited by half a million people.

But at its center is a square mile of unspoiled magic, still home to about 50,000. Ringed by walls of mud, Sanaa's old city is a cramped quarter of earth and stone skyscrapers, teetering eight and nine stories into the air. This daredevil engineering, some of it 800 years old, is matched by a decorative eye that is almost psychedelic. The buildings have become canvases for giant finger paintings, with sweeps and swirls and squiggles of gypsum and mud. Light filters in through windows of stained glass and alabaster, and the towers are topped by misshapen crowns that resemble candle drippings. From certain angles the whole town seems tipsy.

"They looked like surviving entries from an ancient sandcastle competition," concluded the English writer Jonathan Raban, who labeled Sanaa's architecture "mad mud-Tudor."

At ground level, the old city is a tangle of cobbled alleyways that defies navigation. All lanes lead eventually to the souk, a sprawling, open-air bazaar of spice merchants, bread mongers, brass beaters, weavers, milliners, bookbinders and tinkerers in a score of lost or forgotten trades. It is small wonder that the Italian director Pier Pasolini chose Sanaa as the set for a film version of "A Thousand and One Nights."

"Mister! Mister!" a dagger merchant cries, pressing a blade against my finger to show how sharp it is. "For you a very fine jambiya." Nearby, a woodworker carves small, training jambiyas for Yemeni boys.

A camel, blindfolded to keep from getting dizzy, plods in a tight circle around a wooden mill, churning sesame seeds into oil. Blacksmiths heat ore in hellish open furnaces, then beat the metal on broad black anvils, their sledgehammers sending sparks into the street. Women walk past in brightly colored veils that conceal everything, even the eyes, so that the market seems full of tie-dyed Halloween ghosts. When the women stand still, the direction of their toes is the only way to tell back from front.

And the traveler walks through it all seized by a panic peculiar to Arabian souks -- that a magical spot, once discovered, never will be found again.

"The Turkish bath? Go to the silversmiths and turn left," a nut seller says, stirring cashews in a giant wok. "It's just around the corner." Which corner? What silversmith? Left from where?

By the third or fourth visit, the bazaar's geography begins to unfold. Like all souks, Sanaa's is divided into submarkets according to specific goods. Even jambiyas have their own district, as do other items rarely found outside the Arab world: veils, embroidered pantaloons, water pipes, Korans.

But Sanaa's market is idiosyncratic, like everything in Yemen. At other Arab markets, a seller names his price, a sensible buyer offers half as much, and the two sides haggle until they reach a compromise.

Not at Sanaa. Here, even the most practiced histrionics will fail to budge a shopkeeper from his sticker price. The dismissive laugh, the plea of poverty, the flattery, the casual exit -- forget it. A Sanaa craftsman will shift his qat cud from one cheek to the other, shrug and keep on tinkering.

"Why should I lower my price?" an embroiderer asks, looking bored. "The man next door will charge the same. You like this dress. You will pay."

He is right, and as soon as the buyer pays, the embroiderer offers him a fistful of qat as compensation.

"Chew this and you will not care that you have just paid too much," he says, returning to his needle and thread.

Chew qat and you will stop caring about many things.

One day, a millennium or so ago, a sleepy goatherd noticed that his flock became playful and lively after grazing on a roadside shrub. The boy sampled a few leaves, felt much the better for it, and qat has been sweeping through Yemen and East Africa ever since. Or so the legend goes.

Today, qat is North Yemen's cash crop and national dish. Mornings are given over to picking and peddling qat; afternoons to eating it. "Qat is the oil on which the society runs," says an American aid worker in Sanaa, who, like many foreign workers in Yemen, chews the shrub on a daily basis.

But Yemenis are junkies of an unusual sort. Their addiction to qat is more social than physical. In a culture that prohibits alcohol, and whose life is still centered on the village and home, the afternoon "chew" is a kind of enforced sociability -- what tea time is to the English, or a pub crawl to Australians. To abstain from qat is to step outside Yemen's main social rhythm.

"When I stopped chewing, it was like someone had taken my passport away," says Mansour Shamiri, a government worker who kicked the habit after studying in the United States for three years. "There was nothing to do, no one to talk to."

Mansour has since resumed the habit, and one day after work he invited me to chew at his home in Sanaa. Like most Yemenis, Mansour maintains a special chamber for qat sessions, called a mafraj. This ersatz dining room is laid out so that chewers can sit in a circle, reclining on pillows and sharing a water pipe, called a "hubble bubble." Women hold their own chews in more modest quarters.

Qat parties typically are BYO, so I stopped off at Sanaa's sprawling qat souk on the way to Mansour's. To me, the shrubs on offer at a thousand or so stalls all looked about the same; some a bit redder or lusher, but if you've seen one bush you've seen them all.

To the practiced eye, though, two qat plants can be as different as, say, Gallo and Mouton Rothschild.

"This one from the north, very good," Mansour declared, inspecting one of my bushes. "This one, nothing special." He guessed, correctly, the exact price I had paid for each (an afternoon's supply costs about $15). Three guests arrived and they, too, began a careful inspection of the luster and fullness of each other's shrubs. Then, without ceremony, they began picking at the tenderest leaves and shoots and stuffing them into their mouths.

At first the leaves had little effect, other than causing me to gag and spit as they caught in my throat. My companions, meanwhile, seemed to have no trouble chewing, chatting, smoking tobacco and sipping Pepsi all at once. I felt as if I were competing in some odd, oral decathlon.

After an hour or so, when I'd finally managed a reasonable cud, a curious sense of well-being began easing up from my toes. I felt as if I'd had a few cappuccinos, spiked with whiskey, but without the sharp edge of coffee or the fuzziness of alcohol.

"Quayes," the turbaned man beside me kept saying, pointing to his head. Quayes is Arabic for "good" or "feeling fine." Yes, qat quayes, I mumbled back, and kept on chewing.

Luckily, my host spoke English and we vaulted right past small talk and straight into politics, religion, qat, culture, dreams, qat, fears, fantasies, qat. I felt as if every time I opened my mouth, the most perceptive comment ever made on the chosen topic would invariably spill out. A tape recorder, no doubt, would tell a different story.

Mansour also was feeling rather expansive. In a typical flight of qat-fancy, he explained to me a hidden truth: Everything in the world originated in Yemen. Turkish steam baths were invented here, then stolen by the Ottomans. The Santa Fe style began with the mud brick buildings of Yemen, long before it reached the American Southwest ("My people travel a lot," Mansour hypothesized. "Maybe a Yemeni conquistador.") Even Yemeni Jews are "the real ones" because they came here in the first diaspora after the fall of the temple in Jerusalem.

"William Shakespeare came from here, too," Mansour concluded with a flourish. "His real name was Sheik Zubayre, a very common name in Yemen. The English changed it."

We laughed, chewed qat, and kept on chattering.

At dusk the babble gave way to a warm meditative glow. One man stared out the window, another puffed meditatively on the hubble bubble. And the mafraj looked like a freshman dorm after an all-night party: qat leaves all over the floor, ash trays and spittoons filled to overflowing, and smoke so thick that lamp light bounced off it like high beams in fog.

I asked Mansour how Islam could permit such a custom to flourish. It was the sort of exchange, between Arab and Westerner, Moslem and Jew, that could never have occurred outside a qat chew.

"Actually, Islam is of two minds about qat," interjected his brother, Abdul, a scholarly man who had spent most of the day puffing tobacco through the hookah's 15-foot hose.

When qat first became popular, he explained, Arab mystics claimed that the plant brought them closer to Allah. Opponents said it was an intoxicant, like alcohol, and should be declared forbidden or haram. In the end, scholars from Mecca mediated the dispute and ruled that qat chewing should be permitted, but not encouraged. They labeled the shrub "a doubtful substance."

"Doubt is okay," Abdul said, picking the last leaves from a well-stripped qat bush. "It's not like marijuana. Now that's a drug."

The qat chew ended as unceremoniously as it had begun. We rose, thanked our host and headed into the cool and starry dark.

Standing outside, breathing in the thin air of a winter's night in Sanaa, with its mud walls and mud towers and mountains girdled 'round, everything real seemed unreal, and everything fantastic seemed, at least for the moment, worth entertaining. Even the Yemeni bard, Sheik Zubayre. Tony Horwitz is a free-lance writer based in Cairo. His first book, "One for the Road," will be published in June by Random House.

WAYS & MEANS

Touring North Yemen requires an above-average sense of adventure, and an even higher tolerance for squalor and discomfort. There are few modern conveniences in the cities and none at all in the countryside. English is a rare commodity. And apart from a few museums and mosques, there aren't many "sights" in the traditional sense. What Yemen offers instead is a glimpse into a world that has little in common with the West, and one that vanished decades ago in most other Arab countries. A walk through the market, or souk, is usually the best way to take it all in.

Sanaa, the capital and main point of entry, is arguably the most colorful city in the Arab world. Founded before the 1st century A.D., the city was fortified by a mud wall, of which a few samples remain. Enter through the only surviving gate, called Bab al-Yamen, and get lost; you will anyway. Sanaa is seventh heaven for architecture buffs and also for shoppers: jewelry, daggers and clothing are the strong points of the Sanaa souk. The national museum is also worth a look.

GETTING THERE:

There are no direct flights from the United States to Yemen, but connections can be made through major European cities. Lufthansa offers a $1,524 round-trip excursion fare that includes a flight from Washington, D.C., to Frankfurt on Lufthansa and a connecting flight to Sanaa on Yemenia airlines. The fare is restricted to trips of 14 days to three months.

VISAS:

A visa is required to visit North Yemen and is available from the Embassy of the Arab Republic of Yemen, 600 New Hampshire Ave. NW, Washington, D.C. 20037, 965-4760. As in some other Arab countries, mentioning that you're Jewish on the visa application can create complications. Similarly, holders of passports stamped by Israel or South Africa will encounter problems.

GETTING AROUND:

You will need a government permit to travel within North Yemen. Permits are free and are available upon arrival in Sanaa from the General Tourist Corporation at the western end of Tahrir Square. Be prepared to present your passport and to list the towns and villages you wish to visit. Hours: 8 a.m. to noon.

At most hotels, it is easy to hire a car and driver for day trips from the capital. One of the best trips takes in the mountain villages of Kawkaban and Thilla, and a spectacular valley called Wadi Dhahr. Sanaa and environs are worth at least three days.

Going farther afield requires planning: The roads are poor and the drivers worse. Rental cars can be found at two agencies in downtown Sanaa, but be prepared to pay a hefty cash deposit for dubious vehicles. A four-wheel-drive car will cost about $50 a day, plus gas.

Other options include tour buses, flights to the major towns and overnight hire of a car and driver at the hotel. Translators and tour guides also can be arranged through most hotels.

A few words of caution: Far less English is spoken in Yemen than in other Arab countries, and navigating through the countryside can be particularly challenging. Also, Yemeni women are heavily veiled; Western women will encounter few problems if they are conservatively dressed.

EXCURSIONS:

Which direction you go from Sanaa depends on what you're after. For archaeology, go east to the ancient ruins around Marib, once home to the Queen of Sheba. For some of the best mountain scenery this side of Peru, drive west from Sanaa toward Hudaydah, or south to Ibb, Jibla and Taizz. Or do a three-day circle -- Sanaa to Hudaydah to Taizz to Sanaa -- that takes in mountains and the African-influenced coast with its grass huts, unveiled women and men beating drums. On the coastal road, the market at Bayt al Faqih and the city of Zabid are particularly recommended. But this region, called the Tihama, should be avoided during the hot, malarial summer. The rest of Yemen is mountainous, with warm, dry days and cool nights through most of the year.

Finally, there's the road north from Sanaa, into tribal areas that are only partly under government control. This is the least-traveled part of Yemen and the most traditional; recommended for the intrepid. The reward, at the end of a rugged six-hour drive, is the city of Saada, which is a scaled-down version of Sanaa: fantastic mud buildings and the best silver souk in Yemen. It is here that you will find most of the country's Jews.

WHERE TO STAY:

In Sanaa, the Sheba Hotel, or Taj Sheba, is one of the best hotels in the Middle East -- an unlikely outpost of luxury near the city center. Ask for a room with a view of the old city. Doubles run about $100.

The Sheraton also is very good, but far less convenient. On the plus side, it serves alcohol at one restaurant, which the Sheba doesn't, and the Indian food at one of its other eateries is about the best fare in Yemen. The silver shop also is excellent, though expensive. Room rates are similar to those of the Sheba.

In Taizz, the Marib is the best hotel, followed closely by the Plaza and al-Ikhwa. All are a cut below Sheba and Sheraton standards, but so are the prices: doubles run about $50.

In Hudaydah, the Ambassador is simple, clean and a big cut above the other offerings in this rather dismal port city. It also serves alcohol and has a good restaurant. Doubles run about $50.

In Saada, the Rahban is a no-star hotel where friendly service makes up for rooms that are glorified campsites. Prices to match: doubles run about $15. That's as good as it gets in the north.

Reservations are advisable in Sanaa, Taizz and Hudaydah. Credit cards are useless outside the top hotels.

WHERE TO EAT:

Alcohol is illegal in Yemen, though a few of the better hotels sell it in their restaurants. Elsewhere, discreet inquiries at the desk may uncover a bottle of bootleg whiskey. Qat is both legal and ubiquitous, and best consumed after a heavy lunch. Invitations to a chew will be constant and should be accepted. You can eat on the street for less than $5 throughout all of Yemen, but be warned: The country is thick with parasites. As a general rule, stick to cooked foods and don't go near the water.

For a taste of Yemeni cuisine outside the hotels, the Alhalwani on Zubayre Street, the main commercial drag in Sanaa, is tasty, cheap and safe. At lunchtime, the adventurous should find a streetside cafe' that serves salta, a Yemeni stew that is served in a sizzling hot pot with bread. At breakfast, a bean dish called fool is obligatory throughout the Arab world.

In Taizz, be sure to try the restaurant behind the al-Ikhwa, which has excellent Yemeni food and a spectacular view of the mountainside city.

In Saada, eating is inexpensive, and at your own risk. The phobic or tender of stomach should eat at the cafeteria at the Al Salaam Hospital.

INFORMATION:

Embassy of the Arab Republic of Yemen, 600 New Hampshire Ave. NW, Washington, D.C. 20037, 965-4760. Once in Yemen, contact the General Tourist Corporation, at the western end of Tahrir Square in Sanaa, for tour permits and maps.