o one knows just how many people live in Istanbul, since migrants arrive daily, but everyone agrees that the figure must be at least 12 million. It dwarfs most Western European cities, and is probably older than any of them. At its back lie the lowlands of Thrace, on which Istanbul closes its gates. Instead it looks east to the hills and mountains of Asia, whose snows gleam invitingly on winter days.

stanbul is a city absorbed in constant contemplation of an enigma, so much so that sometimes it doesn't know itself. Is it Oriental or Occidental, secular or Muslim, ugly or beautiful, rich or poor? Here the arrogant certainty of New York or London is lacking. Its inhabitants regard their city with an appealing ambiguity and perplexity, yet it surely has as much to offer as any other on earth. The skyline of the old city still takes the breath away (and one notes with gratitude that no modern structures have been allowed to challenge the supremacy of Hagia Sophia and the Mosque of Suleiman). The Bosporus is still an azure ribbon or rope twisting between wooded hills, villas and palaces.

It is true, of course, that this busy strait is crossed by two suspension bridges, but the assertion that Istanbul is ''a bridge between East and West'' is likely to provoke tired smiles or theatrical yawns among natives of the place. Since it ceased to be the capital of great empires (as it was from the early 4th century to the early 20th century), since its grandiose embassies were reduced to consulates and the ambassadors suddenly found themselves marooned in the provincial boredom of Ankara, Istanbul has been very much a city on the edge.

But if Istanbul is on the edge, what is it on the edge of? The answer is both obvious and riddled with paradox. What the Austrian poet Ingeborg Bachmann said of Vienna (twice besieged by the Turks, who thereby inadvertently introduced coffee and percussion music to Central Europe) is surely a hundred times more true of Istanbul: ''The breath of Asia is beyond.'' But here we enter a territory that has been mythologized almost out of recognition. By Asia (I am excluding the Far East) we mean emptiness -- dead civilizations, mud-built villages, thin poplars, elusive crossing points of vast migrations and invasions; and, more specifically, we mean central Anatolia, where no middle-class citizen of Istanbul would be caught dead. So Istanbul continually confronts what it is not: emptiness, migration, impermanence. It follows that its mood is at once deeply rooted in its imperial past, and the sheltering presence of its architectural heritage, and at the same time as volatile and fickle as the winds that blow through it. (In ''Istanbul, the Imperial City,'' John Freely identifies no fewer than 27 such winds or storms, each with its distinctive name, ranging from the Storm of Roasting Walnuts to the Storm of Mating Rams.)

In Istanbul you must orient yourself in time as much as in space. A brief stroll can take you from the 19th century through the 16th to the 6th (though not necessarily in that order). It is a deeply layered city where you should walk carefully and respectfully, since you can never know what lies beneath your shoes. Just recently, for example, while wandering in streets behind the Blue Mosque, I stumbled on the enormous vaulted substructures of a Byzantine palace directly under an expensive carpet store. Maps will give you the broad outlines of the city, but the mystery, as usual, is in the details, and the street I live on goes unmarked. Even the name of my neighborhood furrows the brows of taxi drivers. I have to tell them it is ''near the Galata Tower,'' and this is how you should find your way about, steering yourself according to monuments, and glimpses of what the sixth-century poet and historian Procopius referred to as the city's ''garland of waters.''

Your excursion might take you to the deeply religious quarter of Eyup, where huge flocks of pigeons swirl above the domes of octagonal tombs, or the teeming concrete underpasses of Eminonu, where you could find yourself buying something you never knew you needed, or you could take a leisurely ferry to the Princes' Islands, where plane trees shade the cool streets, and the only vehicles are horse-drawn phaetons. The oleanders of the islands are a promise, but one we don't keep often enough. Because of them we never feel hemmed in. Because of them, the door to the balcony is always ajar, and the view is limitless.

n Turkey idleness is not a sin, indeed it is an essential element of keyif, a word my dictionary translates somewhat inadequately as ''pleasure or delight.'' An extraordinary amount of time is spent sipping tea and playing backgammon in cafes, or loitering in restaurants over the prodigious variety of appetizers known as meze, the point being to extend keyif for as long as humanly possible, or at least until the waiters start to yawn and talk among themselves.

Although there are complex subcategories, most Turkish restaurants fall under two headings -- lokantas and meyhanes. The former are essentially lunch places serving good, plain food to workers. Alcohol is rarely available, and menus are for the uninitiated. You simply walk up to the steam tables where the food is displayed, and pick whatever you like the look of. There will be succulent soups (recommended for colds, flu or hangovers), stewed meats and vegetables (okra, spinach, chard, eggplant) and fresh green beans and white beans in tomato sauce. And your choice will be on your table almost before you've had time to sit down.

While it is true that you can find any kind of cuisine you might desire in Istanbul, from Korean to Iberian, served in settings that range from the rudimentary to the drop-dead elegant, if you want to understand the soul of the city a long evening in a meyhane is obligatory. In discussing meyhanes we aren't just talking about food, but about the exuberant expression of an entire way of life. Meyhanes, which serve alcohol, tend to come in clusters, and in Kumkapi and Beyoglu there are whole streets of them, all vying with polite desperation for your custom. Weaving your way between gesticulating waiters and itinerant musicians, your party (which should ideally consist of at least six people) will soon find a table, and you should immediately order rakis all round. Raki is the legendary, Turkish anise potation that destroyed the liver of the great Kemal Ataturk. Since it also indirectly caused the death of Orhan Veli -- the greatest poet of meyhane culture, who once wrote ''I should have been/A fish at the bottom/Of a bottle of booze'' -- it should be treated with deep respect. As soon as your drinks have arrived, a waiter will swoop toward you balancing an enormous, round tray heavy with meze. This is why you will need at least six people, to appreciate the full panoply of flavors, from lakerda (pickled fish with red onions), through roasted, sweet red peppers to semizotu (purslane in a yogurt and garlic dressing).

As the evening progresses your main course -- often seafood, such as shrimp baked in a casserole or whiting, battered and fried and served with arugula -- may come to seem less and less important, and you should postpone ordering it until the last minute, since its arrival signals the beginning of the end of keyif. Toward the end of the evening in a meyhane, any number of things may happen, but, despite the amount of raki consumed, drunken boorishness is very rare. Musicians are usually within earshot, so perhaps a group of women (out on the town without their menfolk) will rise to their feet, urged on by the shrill squealing of a zurna (a kind of elongated clarinet) and the clatter of a hand-drum and indulge in some impromptu belly-dancing. And yes, it is quite likely that they will dance on the chairs and the tables, but they will do so with a surprising decorousness. It is even more likely that an entire table will burst suddenly into song, and will soon be joined by neighboring tables exchanging deftly harmonized verses. The song will be infinitely melancholy, but one should not conclude from this that Istanbul is a city of depressives. Their native wisdom urges the Turks to embrace sadness as an inevitable concomitant of living. At such moments, everyone in a meyhane is at one with the spirit of Orhan Veli as he sat by the Bosporus overcome, for no particular reason, with an ''indescribable sadness,'' and sang his song to the city he called ''my lover, my fever.''

hen we think of Turkish style we think of Iznik ceramics, kilims, carpets and hamams, but we are living in the past, which is not where most Turks want to be. Good quality kilims are still being produced, but it is mostly foreigners who buy them, and rugs can't tell us much about the style of contemporary Istanbul.

A style only becomes identifiable when it becomes self-aware, and something to aspire to. All it takes is a few cafes and bars where like-minded people can sit and talk and listen to the same music, and feel that they are -- well -- onto something, even if they aren't sure precisely what it is. In the last five or six years all of these factors have come together in a small, central district of Istanbul, which, for purposes of simplicity, I will call the Tunel. This name, which derives from the fact that the district is home to the world's shortest subway line, covers many diverse quarters with difficult names. It forms part of the Ottoman European quarter of Pera-Galata, and stands on a steep hill overlooking the Golden Horn and the old city. For decades it suffered from decline and neglect as the original, polyglot population, consisting mostly of Greeks and Jews, began to drift away, and was replaced by poor, rural migrants. It was no longer a place where the middle class wanted to live. As a result, it entered the 90's with the vast majority of its splendid Beaux-Arts and Art Nouveau apartment buildings intact, at which point it began to benefit from the growing cultural maturity of republican Turkey, a maturity that involved a certain disenchantment with modernity. One fin de siecle was joined to another. Why live in a banal box miles from the city's historic center when you could rent or buy an authentic late-Ottoman apartment with stuccoed ceilings and the projecting window bays known as cumbas, whose origins can be traced back to Byzantine times?

The pioneers of this movement, which is both a return and an advance, were artists, intellectuals (some of whom had never left) and foreigners -- the usual suspects, you might say. Small art galleries soon opened, and groups of young artists took to staging exhibits in derelict buildings. Cafes and bars sprang up overnight, ranging from the funky and friendly Babehane to the ultrastylish, and expensive, New Pera, with its spectacular roof terrace. The seal was set by the opening, just off vine-shaded Sofyali Street, of a fashionable club called Babylon.

Although impeccably cool, Babylon is not just a place where you go to see and be seen, it is home to some very serious and sophisticated music making. Indeed, the whole neighborhood seems to be gripped by melomania. Galip Dede Street, which begins with a Mevlevi dervish lodge, is otherwise given over to stores selling ouds, zithers, synthesizers and sound systems. In cafes and bars you will hear jazz classics (especially early Miles Davis and Chet Baker), acid jazz, hip-hop, house, rai, trip-hop, techno, in fact just about anything other than the groaning behemoths of white, Western, male rock.

The new generation of British-Asian musicians -- Nitin Sawhney and Talvin Singh, for example -- are also increasingly popular. This gives us a clue to what is going on here. Istanbul has an enormously rich and diverse musical tradition, and it is also a city that has long taken a passionate interest in jazz. A hybrid was perhaps inevitable. After all, improvisation and a certain soulful melancholy are common to both traditions. So we find Burhan Ocal's Istanbul Oriental Ensemble collaborating with black musicians from New York and Philadelphia, or Brooklyn Funk Essentials blending seamlessly with a (mostly) traditional Gypsy band called Layco Tayfa. These musicians, along with many others, have recently been heard at Babylon. The groove runs deep, and Istanbul is fulfilling its ancient role as a cultural meeting place with a new -- or recovered -- sense of confidence and flair.