Well, to be honest there is no city center in Istanbul. Everything is spread quite even. However there are 2 areas which attract tourists the most: Sultanahmet and Istiklal.
If those attract a lot of people, it'd be great (from government point of view) to also deploy additional police and police heavy cars. In case someone starts to protest they already have everything in place. Quiet convenient.
Hagia Sophia is something you simply can't skip in Istanbul. Architecture and interior completely blew my mind. Then I learned it was build just in 5 (five!) years in 6 (sixth!) century and I denied to believe it. That's just impossible. However it happened.
I wasn't lucky: Sultan Ahmed Mosque was partially unavailable due to renovation works, but Süleymaniye is very beautiful. The city of amazing mosques.
Don't forget about cats. They are still here.
Turkish coffee. You can try (almost) any cafe out there and it will be just great.
A bit of political agitation.
Local stadium. I can't say Turkish people enjoy sport a log, but they like football (at least to support the game). Smoking the also like. There are a lot of people with cigarettes on the streets.
Streets are so cozy in Chora Church area. The walk was very enjoyable and pretty. Even though there were some semi-ruined blocks it was wonderful.
It's always so hard to pick just a few photos from dozens I make. Here two more.
Finally I've managed to the bridge. There were so many seagulls, I can't even tell whether I've seen so many at once before.
A fence. They even put a tram behind a fence (:
Istiklal walking street. In Sultanahmed area everything goes to sleep in the evening. Here evening is a beginning of life. Tons of cafes, discos, people. Not everybody loves it, but it's interesting to walk here at least once to watch what's going on.
There are lots of street musicians on the street. I don't remember any exceptional guys though.