Nightclubs
While there are night clubs all over the city, two of the hottest clubs of istanbul are in ortaköy.
Beyoğlu is notoriously known for its night life; it's full of cafes and bars with live music. People from all classes and ethnicity can be found here.
Nişantaşı is the place for young entrepreneurs and artists, the prices are higher than Taksim.
Kadıköy also has a nightlife scene, serving mostly locals of this part of the city. It is usually has more easy-going style of nightlife, usually with local pubs and wine houses and traditional meyhanes. If you are not staying on that side of the city, it may not worth the trouble to make an inter-continental trip just to have a drink, but drop by if you are around and thirsty.