Istanbul is full of terraces with beautiful views of the city and the Bosphorus, where you can just come to drink tea, smoke a shisha with friends or eat there.

Konak Cafe

But there are also private terraces, with breathtaking views!
One night, a Spanish friend took me to his friend's house near the Galata Tower, the apartment has a huge rooftop with the most beautiful night view that I saw of Istanbul for now. It was fascinating to see Istanbul and the Bosphorus from this perspective in the dead of the night.

But my favorite is still the one near the Suleymaniye Mosque. It offers wonderful view over Istanbul, at sunset the colors become unreal and seagulls are playing models.