The fantastic city Istanbul lies on the two sides of Bosphorus, that seperates Europe and Asia. In most of the major cities in the world, there is a river flowing through the city; but in Istanbul it is a sea that flows through, which is “blue” and wide unlike others; that makes Istanbul unique and to-be-seen.
Istanbul is a major city, with a population of nearly 20 millions and area of 6000 square kilometers. Throughout the history, Istanbul had been the capital city of the Roman, Byzantine, Latin, and Ottoman Empires. The city was chosen as joint European Capital of Culture for 2010. The historic areas of Istanbul were added to the UNESCO World Heritage List in 1985. This huge city lies on two continents; Asia and Europe, connected with two bridges over the Bosphorus. Basicly, the Asian side is said to be residential, while the European side is both commercial and residential. Since real estate values are higher in the European side, people tend to live on the Asian side and work on the European side, dispite the heavy traffic on the bridges in rush hours.
Istanbul consists of 31 districts. As in all major cities, the central districts are the most popular and touristical ones. I will be giving details later, but the most popular ones are the Historical Peninsula, Beyoglu and Besiktas (the most popular region of residence, commerce and entertainment). On the Asian side the Kadikoy district (the peninsula between the Bosphorus and the Marmara Sea) is a nice neigbhorhood, especially the Bagdat Avenue.
You can also get official information from Istanbul Municipality web site