Istanbul is such a diverse city that it's almost impossible to split it up into definable districts. The only real distinction that can be made is between the European and Asian sides, which are separated by the Bosphorus Strait. Stretching from the Black Sea, straddling across the Bosphorus, touching the Sea of Marmara, Istanbul, with an estimated population of between 10-13 million, has become a city of unlimited scope.

Sultanahmet

Most people who come to Istanbul land feet first in Sultanahmet. This peninsula (known as Sarayburnu) juts out into the Bosphorus, the Golden Horn and the Sea of Marmara. Rich in history, it's a natural magnet to millions of tourists every year. The home of Topkap? Saray? (Topkap? Palace), Ayasofya (Hagia Sophia), the Blue Mosque (Sultan Ahmet Mosque), Yerebatan Saray? (Yerebatan Basilica Cistern), and the At Meydan? (Hippodrome), Sultanahmet is filled to the brim with hotels, restaurants, cafes, bars, rug stores and cheesy souvenir shops, as well as a plethora of fascinating museums, mosques, markets and historical sites. The main drag, Divan Yolu, is the heartbeat of the area, and there are hundreds of tiny back streets and alleyways to explore the history of the old city. The labyrinthine Kapal?çar?? (Grand Bazaar / Covered Bazaar) near Beyaz?t University is also on this street. Sultanahmet can be a little intimidating as it is truly catered to only tourists. (Read: you'll have to learn quickly not to respond to "Hey! Are you American / English / German / Spanish / Italian / French?") One impressive thing about Sultanahmet is that the businessmen each seem to speak every major European language, so if your Turkish isn't up to par, don't fret.

Eminönü

Situated right on the waterfront on the Golden Horn, Eminönü is the end of the tramline. It is generally buzzing with activity during the day, with street peddlers selling you things you never even knew you wanted. The vast M?s?r Çar?? (Egyptian Spice Bazaar) is the main feature of Eminönü Square and Mimar Sinan's Yeni Camii (New Mosque) is a familiar landmark with its minarets standing tall above the general chaos. Ferries to the Asian side and the Princes Islands leave from the huge docks lining the shore, where you can stop by and have a fresh fish sandwich (bal?kekmek) while you wait for your vessel. The Sirkeci Train Station is also here: all trains to and from Europe begin and end their journeys here.

Beyo?lu / Taksim

A veritable symphony of occident and orient, Beyo?lu is the pulsating heartbeat of Istanbul's day and nightlife. ?stiklal Caddesi -- a paved thoroughfare perpetually swarming with Istanbul's colourful hoi polloi -- is at the hub of the metropolis while a maze of narrow winding lanes filled with funky cafés, soulful bars, continental restaurants, historic cinemas, prominent theatres and exclusive shops shoot off in all directions around it. Taksim Square, featuring the impressive Monument to the Republic, leads the way into Beyo?lu's bohemian open-air museum, past the Greek Orthodox Aya Triade Church and the French Consulate. A quaint old tramway carries passengers past the Rumeli Han, Çiçek Pasaj?, Cite de Pera, Atlas Pasaj?, Galatasaray Lisesi, and several elegant consulates. Every year the International Istanbul Film Festival, International Istanbul Music Festival, International Istanbul Theatre Festival and the International Istanbul Jazz Festival are held here and in nearby districts. Beyo?lu, which has been the traditional home of Istanbul's gay community, hosts various other annual events, including the Bosphorus Festival, Roxy Music Days, Aksanat Jazz Festival and the Blues Festival.

Tünel

This is undoubtedly Istanbul's "Bohemian Quarter," which not so long ago was perceived as a bad part of town, with its dark deserted streets and creepy abandoned buildings. However, the area has undergone tremendous development in recent years. Tiny cafes, live music venues, and open-air restaurants and bars now quietly coexist with art galleries, antique bookshops and music stores.

Karaköy

Around the first century BC, there was a tiny village situated on the mini peninsula of the Golden Horn where the modern suburb of Karaköy stands today. These days, Karaköy is a bustling port with a lively fish market, a hectic ferry terminal and a shady nightlife; an intriguing landscape at the mouth of the Golden Horn. Scores of locals fish from the Galata Bridge and an array of vendors peddle all kinds of goods along the sidewalks. A vast underground marketplace where you can buy electrical appliances and guns, among other things, provides not-so-safe passage under the busy road to the entrance of Tünel. Up the hill is Bankalar Caddesi, an historical area filled with banks, art galleries and do-it-yourself stores. All visiting international cruise ships dock in Karaköy.

Galata

The Genoese-built Galata Tower is the most central point here. The renowned Turkish film Istanbul Beneath My Wings tells the story of Hazarfen Çelebi, who flew from this tower with a home-made pair of wings. The main street, Galip Dede Caddesi, is a hub of activity with shops selling musical instruments and antique books, and you'll also find a good dose of tiny local restaurants. The Whirling Dervishes have a home here at the Galata Mevlevihanesi (Dervish Lodge); the Goethe Institute provides locals with a good dose of culture and art; and there are countless mosques, churches and synagogues hidden away in obscure side streets.

Golden Horn

The most interesting part of the Golden Horn district comprises of the stretch of land between Eminönü and Ayvansaray, up as far as Eyüp. The Selimiye Mosque, the Fethiye Mosque and St. Steven's Church grace the shoreline while the Kariye Müzesi (Chora Church) and Mihrimah Mosque are further inland. The old city walls start at Ayvansaray and snake overland to Yedikap?.

Be?ikta? and Ortaköy

Be?ikta? -- which is actually dismally devoid of places to help you paint the town red -- is at the center of the three-way fork that leads up the hill to Levent. Ortaköy, on the other hand, is a bustling suburb on the waterfront. Bubbling over with cafés, bars, restaurants and tea houses, this area is a popular weekend hangout for locals. Ortaköy's back streets are buzzing with handicraft stalls filled with trinkets and souvenirs on summer weekends. This part of town is renowned for its mosque, church and synagogue within close quarters of one another. The Bosphorus Bridge spans the waterway overhead.

Bosphorus: Arnavutköy to Sar?yer

The Bosphorus shore on the European side is lined with Ottoman-style mansions, high society hangouts and fish restaurants. There is only one main road and it follows the shoreline all the way to Zekariyeköy, a popular weekend getaway for the citybound.

Sea of Marmara Coast: Kumkap? to Yediküle

Kumkap? is a distinctly touristy area filled with over-priced fish restaurants and not much else besides views of the sea. The coast road heads out toward the airport past the old city walls and Yediküle Fortress.

Asian Side & Bosphorus: Kad?köy to Anadolu Hisar?

Kad?köy is a quieter version of Beyo?lu with a more subdued atmosphere. The tiny cobbled lanes are filled with restaurants, cafés, bars, cinemas and shops, but most importantly, residents! The Asian side of town is where most Istanbulites live; you'll have a harder time with no Turkish language skills here, but it's worth it to pop over on the ferry and experience a more relaxed way of life. The coast road snakes past Üsküdar, a pretty suburb with plenty of fine examples of Mimar Sinan's work, including the Mihrimah Sultan and ?emsi Pa?a Mosques. Selimiye Barracks (where Florence Nightingale worked during the Crimean War) is up on the hill. Heading toward Anadolu Hisar?, the road winds along the shoreline (which is less built up than that of the European side). There are plenty of parks and trees, outdoor cafés and restaurants and a string of historical buildings to explore including Beylerbeyi Palace, Kuleli Mosque, Kuleli Naval Officer's Training School, Küçüksu Park & Kiosk and Anadolu Hisar?.

Princes Islands

There are four islands in the Sea of Marmara that attract crowds escaping the summer heat: Büyükada, Heybeliada, K?nal?ada and Burgazada. Ferries leave from Sirkeci, Kad?köy and Bostanc? regularly. There are no cars on the islands -- the transport here is limited to horse-drawn carriages. Each island offers plenty of places to eat and sleep, and there are Greek monasteries atop the hills of Büyükada and Heybeliada.

Harbiye-Ni?anta??-?i?li-Mecidiyeköy-Levent

The Military Museum in Harbiye is a good landmark from which to begin exploring Istanbul's business life. Ni?anta?? is the central shopping district, while ?i?li is strictly a business district that goes all the way to Levent and beyond to Maslak. There is now an underground metro linking Taksim with Fourth Levent.

Top 11 Istanbul Hotels