Camlica hill on the asian side is the highest (natural) point of Istanbul. It has an altitude of 288mt. (945ft). Here is a video you can see the view from it. The bridge you will see in this video is the first bridge that connected Asia to Europe (Bosphorus Bridge).
It also looks like this:
On the European side, Sapphire Building, in Levent neighborhood, is the highest peak of Istanbul. It has an altitude of 261mt.(861ft.). It's the 4th highest building in Europe. Here is a video you can see the view from it.
Also, people have recommended the view on galata tower at sunset and topkapi palace as great Istanbul views.
