On my last trip to Turkey I didn't really have time to do anything, but if you happen to be in Istanbul you should definitly get a reservation at 360 (and by reservation I mean it, it wasn't possible for me to get a table for one person, without a reservation)!

It is located in the middle of Istiklal Caddesi (pedestrian area with tons of shops) off of Taksim square on the top floor of an apartment building. After passing thru the mandatory metal detector check on the floor below, you will be led up to the penthouse style restaurant. Just for the amazing view it is worth a visit! But the international fusion kitchen is very good, too. Try and get a table close to the window and enjoy the spectacular view over Istanbul.