The people watching in Istanbul was fun. We Americans tend to congregate only in designated areas, and then mainly for consuming something or other. So I was delighted my first night to see a group of people in the street, dancing. Near as I could tell, they were all passers-by that were sucked into the music.
One of my favorite scenes was at Galata bridge, where scores of fisherman lined up to fish. At night, with the lights of the city catching their fishing lines, it was a sight to behold. Unfortunately, without a tripod, this was the best I could do.
The Grand Bazaar is a great place to wander around for a while, if not to shop.
A boat tour of the Bosphorus was a great way to spend the final afternoon.