I'm not even sure where to begin with Istanbul. It was the reason we picked this cruise. We knew next to nothing about the city before we went, and I'm not sure we know much more now.
Istanbul is massive. It smells good - like ocean, flowers, incense and street food. It feels aged and stately and vibrant all at the same time. It is a melting pot, but not in the New York/LA sense of the word; it is a true crossroads of civilization. It's very apparent that Istanbul has seen and heard more human history than one can possibly imagine.
It is stunning. Your eyes will be exhausted from looking at all the Color and Pretty. Istanbul is Stylish. So very, very stylish. I wore my best pair of 7's and a black trench coat with a pretty silk scarf and thought myself well-appointed. Not so. I wish I'd had the time (and means) to purchase an entirely new wardrobe in Istanbul.
And on that note...bring lots of money - you will inevitably want to buy a stunning pair of sparkly brocade ballet flats in the bowels of a subterranean antiques shop on your way back to the port, and you don't want to have to say 'no' and regret it to this day.
Sailing into the Bosporus, we had an amazing view of the Blue Mosque and the Hagia Sophia.