What is the main setting in the novel, The White Castle?

Most of the book's action takes place in Istanbul. Istanbul is the largest city in Turkey and is among the 25 largest urban areas in the world. It is located on the Bosporus Strait and includes the entire area of the Golden Horn, which is a natural harbor. It has also been known as Byzantium and Constantinople before becoming Istanbul after the Ottoman conquest of 1453. The capitol of Turkey, however, is not Istanbul but Ankara.