Most of the tv series are filmed in the mansions on Bosphorus. If you will take a Bosphorus tour the guides will show you the famous mansions.
Also you can see Balat, a historical town where many popular tv series have been shot. And you can go to Bebek, its another popular tv place and has a beautiful seaside there are lots of famous cafes and restaurants too.
If you are interested a specific series, feel free to ask.