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.
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 Topkapı Sarayı (Topkapı Palace, Ayasofya (Hagia Sophia), the Blue Mosque (Sultan Ahmet Mosque), Yerebatan Sarayı (Yerebatan Basilica Cistern), and the At Meydanı (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 Kapalıçarşı (Grand Bazaar / Covered Bazaar) near Istanbul 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. Also keep in mind that bargaining with street vendors or the Kapali Carsi folk is always in order.
Eminönü is a very historical district, which as a result of its secluded location within the peninsula, led to the foundation of Byzantium on this land. The city of Byzantium expanded in all directions from here, leading to the formation of the oldest neighborhoods of Istanbul along the Golden Horn. Situated right on the waterfront on the Golden Horn, Eminönü is a tourist hub, as well as local folks' commercial district, which can easily be accessed with the tram that runs from Kabataş to Zeytinburnu or with vessels that provide public transportation between the two continents of Istanbul. Eminönü is generally buzzing with activity during the day, with street peddlers selling you things you never even knew you wanted or things you never knew existed. The vast Mısır Çarşı (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. Inside the Spice Bazaar is a well known and cherished old Turkish restaurant, the Pandeli, which has been visited by great men and women of all times -including Audrey Hepburn and Queen Elizabet the Second in 1971. 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 (balıkekmek, a.k.a "fish & chips") while you wait for your vessel. The Sirkeci Train Station is also here: all trains to and from Europe, as well as the famous Orient Express, begin and end their journeys here.
Beyoğlu / Taksim
A veritable symphony of occident and orient, Beyoğlu is the pulsating heartbeat of Istanbul's day and nightlife. İstiklal Caddesi -- a paved thoroughfare perpetually swarming with Istanbul's colorful 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 theaters and exclusive shops shoot off in all directions around it. Taksim Square, featuring the impressive Monument of the Republic, leads the way into Beyoğlu's bohemian open-air museum, past the Greek Orthodox Aya Triada Church and the French Consulate. A quaint old tramway carries passengers past the Rumeli Han, Çiçek Pasajı, Cite de Pera, Atlas Pasajı, 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. Beyoğlu, 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 / Beyoğlu
The Tünel or the Tunnel District, is not far from its mainland Beyoğlu, but can be considered as a separate district given its exquisite and original character, soul and atmosphere. The Tünel 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, as well as many designers' boutiques and design hotels. A narrow side lane, Asmali Mescit Street, has now become the representative and popular bar scene face of the district. For many in the city, this street is the only pulsating center on any given Friday and Saturday night. With a variety of open-air bars, such as Otto, Groove, House Cafe and Lokal, people tend to hang around on the street with their coats and drinks. As such, it has also become impossible to walk casually through this bar street lately.
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.
The Genoese-built Galata Tower is the most central point here. With its conical-capped tower head, the Tower dominates both the skyline and the entrance to the Golden Horn from the Bosphorus. 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, most of which won't be serving alcohol and will closed for the night -nevertheless a must try for their expertise in cooking and the taste of local food. 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 is a historic inlet of the Bosphorus and a superb natural harbor that has sheltered many Greek, Byzantine, Roman and Ottoman ships for thousands of years (Wikipedia). The most interesting part of the Golden Horn district comprises of the stretch of land between Eminönü and Ayvansaray -towards the southern shores of the Horn, up as far as Eyüp. The Selimiye Mosque, the Fethiye Mosque, Sepetçiler Kasrı (the Kiosk of of Basket Weavers, now the International Press Center) 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 Yedikapı. During the Byzantine era, the mouth of the Horn was closed by a great chain during times of siege and threat. The great chain would extend from Sarayburnu to the Castle of Galata (which would be in Karaköy in modern times). Mehmet the Second, who conquered the city in 1453, managed to bypass this chain by using wheeled platforms hauled by oxens to pull his ships over the heights of Galata into the Horn and thus over the chain.
Beşiktaş and Ortaköy
Beşiktaş is at the center of the three-way fork that leads up the hill to Levent. It is also the first stop for public ferries going up the Bosphorus. The name means "cradle-stone" which stands for the stone brought from Jerusalem by the monk Yashka to honor his church. The Greek counterpart for the name of the village was Diplokion (Two Columns). It may have been either of these two name and stories that may have inspired the Turkish to call Beşiktaş by this name. There are several places of interest in and around Beşiktaş that can be linked to Ottoman fleets and admirals. The major ones include the türbe (tomb) of Hayrettin Paşa, the türbe of Barbarossa, Sinan Paşa Mosque and the Naval Museum. To the inland, Beşiktaş houses a little pretty palace called Ihlamur Kasrı or the Linden Pavilion within the beautiful Ihlamur Park. This palace is where the grandiose era of the tulips were once lived. Continuing up along the Bosphorus coast is yet another palace, the Çırağan Palace, now a hotel; and a few hundred meters away from Çırağan Palace is the Yıldız Sarayı (Palace of the Star) and the Yıldız Park. Ortaköy, on the other hand, is a bustling suburb of Beşiktaş 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. Ortaköy has also recently opened itself for the night life of Istanbul. The locals' pick for a night out, the Anjelique Club sits here next to the world known Zuma Restaurant and Radisson Hotel.
Bosphorus: Arnavutköy to Sarıyer
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 suburban residential area, which is no longer very far away from the city itself. It could well be said that the shore line starts off from where the Golden Horn ends in Karaköy, but there is a distinguishable change of air once one arrives to Arnavutköy and continues along the shore line in the direction of Yeniköy, Tarabya and Sarıyer. For this reason, when the Turkish people think of European Bosphorus or going by the Bosphorus, they usually indicate somewhere along the coast of Arnavutköy and Sarıyer. The coastline here is paved for pedestrians to go jogging or for walking. Recently the municipality has also introduced somewhat primitive sports equipment and facilities for the public benefit. It is very possible to find people walking and working out along the coast early on a sunny day.
Sea of Marmara Coast: Kumkapı to Yedikule
Kumkapı is a distinctly touristy area filled with over-priced fish restaurants and not much else besides views of the sea. Until recently, it was mostly reserved to the Armenian community. There are still several of their churches and community schools in this region. The coast road heads out toward the airport past the old city walls and Yedikule Fortress. Yedikule translates itself as "Seven Walls" into English and does indicate the fortress that once surrounded and protected the city since the Byzantium era.
Asian Side & Bosphorus: Kadıköy to Anadolu Feneri
Kadıköy is a quieter version of Beyoğlu with a more subdued atmosphere. It also resemble Beşiktaş in terms of its commercial activity and daily hectic and busy life. 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 of the local population lives; 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 Şemsi Paşa Mosques. Selimiye Barracks (where Florence Nightingale worked during the Crimean War) is up on the hill. Heading toward Anadolu Hisarı, 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 Hisarı. The part of the shore from Kanlıca to Kuleli is streamlined with mansion like, luxury villas and neighborhoods on the hills.
Princes Islands are an archipelago of six islands, where Istanbulites used to reside during the summers in the old times. There are especially four islands in the Sea of Marmara that still attract crowds escaping the summer heat: Büyükada, Heybeliada, Kınalıada and Burgazada. Ferries leave from Sirkeci, Kadıköy and Bostancı regularly in the summer during day and night to and fro the islands. Also, in summers, there are faster ferries leaving from Kabataş for the islands. There are no cars on the islands and the transport here is limited to horse-drawn carriages. Each island has plenty of unique offers for leisure, sports and entertainment. There are also plenty of places to eat and sleep. Atop the hills of Büyükada and Heybeliada are Greek monasteries with magnificent views of the sea and the neighboring islands.
All of these districts are mostly business and financial centers of the city with a few residential skyscrapers, which social elites habituate in. The Military Museum in Harbiye is a good landmark from which to begin exploring Istanbul's business life. Harbiye is also filled with offices of many small and medium enterprises, most of which are dentists or tourism offices. Not far away from Harbiye is Nişantaşı, which is the central shopping district -the so called 5th avenue of city. Şişli is strictly a business district that goes all the way to Levent and beyond to Maslak, both of which are strictly dominated with office buildings, shopping malls and banks. There is now an underground metro linking Taksim with Maslak.
Ciragan Caddesi No:28 Besiktas
22 Kalpakçılar Caddesi
Asmalı Mescit Caddesi 28
Seyhbender Sokak 3 Tunel-Asmalimescit