Traffic gridlock. The streets heave with revelers in a blare of color and sound. The time: 1 a.m. and the night is still young the place Taksim square. Confused? Wasn't Turkey about Shari'a, a second Iran? A confusion of terrorism, human rights abuses, barbarity? Midnight Express and all that? Yet while Tony Blair's Cool Britannia still debates the wisdom of extending UK licensing laws beyond 11 p.m., Istanbul is partying the nights away at a proliferating range of venues under an Islamic local municipality, Preconceptions are about to be changed.

Istanbul is sightseeing heaven. If you want churches, there are plenty. Mosques? Istanbul has gorgeous mosques, maybe the world's finest. Palaces? In abundance, Bazaars? The biggest in the world. And then there are the fortresses, city walls, underground cisterns, public baths. Whirling Dervish Theaters, islands, parks and museums… It wouldn't be an exaggeration to say that in its sheer volume of things to see, Istanbul rivals Rome, Paris or London.

But there's little logic to how it's all laid out. No grand masterplan. The topography doesn't help, involving numerous hills split between three landmasses, two on the European side of the Bosphorus divided by the Golden Horn and one on the Asian Shore. There's no uptown or downtown or inner circle or any other convenient way to read the city. It's just a matter of learning the districts. Street patterns are irregular, generations of city planners seemingly almost phobic when it comes to straight lines and right angles. Buildings crowd and block sightlines, every now and again opening up to expose a view that takes you completely by surprise. In such a set-up there's no such thing as a wrong turn, only alternative routes.

THE HISTORIC HEART

Most of the sights that could properly be described as unmissable-either because you really ought to see them or simply because you couldn't avoid them if you tried - are in and around Sultanahmet and the Bazaar Quarter, which together constitute the city's historic heart. Most hotels are around here too, but there's not much in the way of bars or restaurants, so at night locals tend to clear out, and leave the place to visitors. The area occupies the highest part of a fat thumb of land that's wrapped around by the Sea of Marmara and the Golden Horn. Its spine is Divan Yolu along which the tram runs. With stops beside the main mosques, bazaars and markets, the tram is the best way to get around this side of the town. It's air-conditioned too, a blessing in summer.

South of Divan Yolu there's little of interest. To the north, market streets slope precipitously down to Eminonu beside the Golden Horn. Here the tram terminates, over the road from the terminals for ferries up the Bosphorus and over to the Asian Shore. Also here are two bus stations; one north of the main road for buses to Taksim Square, one to the south, beside the Egyptian Market, for services up to the European shore of the Bosphorus to Bebek and beyond.

The Golden Horn bisects European Istanbul, but the halves are linked centrally by two bridges, the Galata and, further west, the Ataturk. West of the Ataturk Bridge, still on the south side of the water, is a place where few visitors venture, a grouping of neighborhoods with an overtly Islamic nature, including Fatih, Fener and Balat. Even further west is Eyup, possessing the fine Eyup Sultan Mosque, one of the most sacred Islamic sites outside of Mecca, Medina and Jerusalem.

North of the Golden Horn is the city center district of Beyoglu, Istanbul's West End and the place to play once sightseeing is done. At its heart is Istiklal Caddesi, a broad pedestrianised European-style Boulevard sprouting a tangle of narrow side streets filled with shops, cafes and bars, restaurants and clubs. Developed largely in the late 19th century, it's an area of great character and grandiose architecture, well worth exploring.

At its north end, Istiklal Caddesi empties into Taksim Square. North are the newer districts of Harbiye, Sisli, Nisantasi and Tesvikiye, not 'sight worthy' but possible visits for shopping, eats or entertainment. Further north still, Etiler and Levent are the more prosperous areas of the city where spending your money is a pastime.

All these areas are 'uphill'; downhill along the shores of the Bosphorus area another whole string of small districts, often referred to as the 'Bosphorus Villages'. Places like Ortakoy Arnavutkoy and Bebek are picturesque clusters of attractive wooden villas with folksy shops and markets and open-air cafes and restaurants. There's not much in the way of major sights, but these neighborhoods are definitely worth a wander. They are linked by several bus services or, better still, you can travel up here by ferry (mornings and evenings only).

The Ferry is also the way to go to get over to the Asian Shore. Visitors expecting some significant change in character to mark a hop of continents are going to be disappointed. Knives and forks aren't suddenly exchanged for chopsticks midway across the Bosphorus. Instead, the Asian Shore is a vast dormitory for Istanbulites who commute each day over to jobs west of the water. Not only is real estate cheaper here, but also it's less crowded and more rural than densely urban European Istanbul. The character of the Asian shore is also heavily shaped by large numbers of immigrants from the Turkish provinces.

NEIGHBOURHOOD WATCH

Sultanahmet
Mosques, palaces, museums and lots of hotels all centered on Sultanahmet Square and the Hippodrome. Cafes and restaurants charge a premium among all the stunning history.

Bazaar Quartet
Hard to say exactly where it starts or ends but the core of the bazaar lies in two districts, Cemberlitas and Beyazit, the latter home to Istanbul's main university.

Eminonu
Waterfront transport hub on the Golden Horn at the southern end of Galata Bridge. Includes the old mercantile districts of Sirkeci and hamam-rich Cagaloglu.

Fatih, Fener & Balat
Conservative districts west of Ataturk Bulvari, south of the Golden Horn, considered a bit beyond the pale by sophisticated Istanbulites but with a wealth of fascinating history and architecture.

City Walls
As far west as most visitors want to venture, the walls rule a line from the Golden Horn in the walls rule a line from the Golden Horn in the north to the Sea of Marmara in the south, passing through the working-class suburbs of Edirnekapi, Topkapi and Yedikule.

Beyoglu
Ground zero for consumerism, nightlife, arts and entertainment. Beyoglu is a blanket name for various small neighborhoods including Galata, with its distinctive tower above the Golden Horn, Tunel at the south end of Istiklal Caddesi, Asmalimescit, Galatasaray and Taksim.

Karakoy
At the north end of the Galata Bridge, a formerly seedy port area with a ferry terminal and a small daily fish market.

Besiktas
A major transport hub, downhill and due eat of Taksim Square. It possesses Dolmabahce Palace and a couple of major museums beside the Bosphorus.

Ortakoy
Southernmost of the 'Bosphorus Villages' - suburbs on the European shore. Famed for its weekend craft market and with a pleasant waterfront piazza, though a bit too popular for its own good.

Arnavutkoy
Where every Istanbulite would love to live given the cash. Full of gorgeous waterfront wooden mansions. Plebs can soak up the ambience at a wealth of cafes and small restaurants.

Bebek
For our purposes Bebek, with neighboring castle Rumeli Hisari, marks Istanbul's northern city limit. A fine half-day can be had by taking a bus or ferry up here then walking back via Arnavutkoy to Ortakoy.

Kadikoy & Uskudar
The two main centers on the Asian shore, neither of which is possessed of great monuments or other sightseeing musts, but they make up for it in character and plenty of quirky little corners.