There are a lot of places in Istanbul to visit my friend.Let's start with Anatolian side...You may visit the islands first, there are 5 islands in marmara sea near the mainland;Kinali,Burgaz,Heybeli,Buyukada Islands..There is a monastery in Buyukada if i remember right :) and then you can wander around in Bagdat Street.It's nice and luxury place... I definitely suggest you to have trip on bosphorus :) You may love it ! and there are a lot of historical places like Topkapi Palace,Sultanahmet mosque etc..