Istanbul has a number of districts, each with their own distinct personalities.  It would also help to remember that the city straddles both Asia and Europe, and thus each side is imbibed with its own set of characteristics.  Add to this the fact that there is a major waterway (the Bosphorus Strait) that divides the city into two.  The European side is then further separated from the rest by the Halic, or better known in English as the Golden Horn.
the golden horn
The city itself is divided into three major areas – the historic peninsula (including Fatih and Eminonu), the Kadikoy and Uskudar quarter and the Beyoglu and Besiktas neighborhoods.  These are then divided into smaller districts.  There are actually 27 districts in the Istanbul city proper.

To the south of the Golden Horn are some of the remains of the Byzantine walls and make up what is known as Old Istanbul or the Historic Peninsula.  This is where you will find Fatih and Eminonu.  The more schizophrenic counterparts of Besiktas and Beyoglu are to the Golden Horn’s north.  It’s schizophrenic because it holds a mixture of the old and the new.
Old Istanbul is where you can find most of the vestiges of the empires that were – the Roman, the Classical, the Ottoman and the Byzantine.  This is where you can find the seven hills that figure prominently in the establishment of the city of Constantinople.  Emperor Constantine wanted this city to also be founded on seven hills, just like Rome.

At Eminonu, you will find the smaller districts of Kumkapi, Sultanahmet, Sarayburnu (or Seraglio Point) and Cankurtaran.  Sultanahmet is by far the most popular district, as this is where most of the historic sites are located.  Here you will find the Hippodrome, the Hagia Sophia and the Blue Mosque.  Sarayburnu, on the other hand, is where you’ll find the Topkapi Palace. This is also where the Golden Horn, the Marmara Sea and the Bosphorus meet.  Still in Eminonu, you will find the districts of Cemberlitas, Laleli, Suleimaniye and Divanyolu.
fatih mosque
The Fatih area, on the other hand, is where you will find the Fatih Mosque. Fatih is also home to the following neighborhoods: Eyup, Ayvansaray, Yenikapi, Fener, Balat, Edirnekapi, Yedikule and Sahil Yolu.

Opposite the Old City, across the Bosphorus, are the districts of Beyoglu, Galata, Karakoy, Tophane, Pera and Tunel.  The Beyoglu Quarter is linked to the Old city via the Galata Bridge and the Ataturk Bridge.  It is where you can find structures built in the Belle Époque era.  Galata, meanwhile, is beyoglua neighborhood half-enclosed by the Byzantine walls.  Pera is where you will find the famed hub for Istanbul nightlife, Istiklal Caddesi.  Going further are the quarters of Cukurcuma and Cihangir.  Going northwards from Taksim, you will find more tony neighborhoods, such as Nisantasi, Harbiye and Macka (which is Istanbul’s answer to Wall Street).  The districts facing the waterfront are now relaxing residential areas, when once these were fishing coves.  These residential neighborhoods include Istinye, Emirgan, Rumeli Hisari, Aravutkoy, Sariyer, Rumeli Kavadi and Bebek.

Whew!  There are so many, and that is just on the European Side!

uskudarAs for the Asian side, you will see that these are more about residential neighborhoods, dotted with some mosque and historical monuments.  Here, you can visit the districts of Uskudar, Kadikoy, Bagdat Caddesi, Kanlica and Beylerbeyi Sarayi.