Visit the Ortaköy Mosque
Officially called "Great Mecidiye mosque" you will find it on the maps under its Turkish name Büyük Mecidiye Camii. You will be struck by the sheer elegance and beauty of this mosque which the architect designed along the lines of the Opéra Garnier in Paris. Located at the tip of Ortaköy, which literally means "the village in the middle" it seems to be floating on the Bosphorus; with the bridge in the background it is the perfect place for a photo or for professional photographers.
You can get there either on foot (but it is a bit long and the traffic is dense) or make a stop during your cruise on the Bosphorus; alternatively, do as the locals do and take the bus from Besiktas to Ortaköy. For 3 TL you will arrive in 5 minutes.
Mecidiye Mh., 34347 Beşiktaş/İstanbul, Turkey