If you look at the map you will see that a geological strait
separates the European and the Asian parts of Istanbul. This
strait is called the Bosphorus.
You can see also that the Bosphorus connects the Marmara Sea
in the south to the Black Sea in the north. In the past, this
city had been known as Byzantium and later as Constantinople.
The main district of what was once Constantinople
is now called Sultan Ahmet.
Taksim is the main commercial
center of Istanbul. Remember that this city is so large that
there are many other commercial centers as well..