Asmali Mescit - this is a street that hits istiklal street on the south side (closer to the galata tower, farther from taksim square), and apparently this is where all the youth go out at night. lots of bars and clubs i think, and i’m sure plenty of places to chill and just drink or hookah at night. Cafe Pi (bar) and Vida Pera (more dancing) are both supposed to be pretty cool (I haven’t been myself).