Hey. I went on a safari before and was gone about a month including Istanbul so I packed a bit light as I didnt want to lug around a bunch of gear for a month. I brought my two d7000's and the 17-55 2.8 and 70-200 2.8. THe 70-200 was mostly for the safari and after the two weeks in Africa it didnt come out of the bag for Istanbul or Berlin. I used only the 17-55 2.8 the whole time I was in Istanbul but that was also the only lens I brought. TO be honest I didnt find many times where I wished I had a different lens on the camera. For my style of photography the 17-55 was fine.
If I was to go to Istanbul and that was my only destination and I could bring more gear then probably the only other lens I would have brought would have been a fast prime like my 35mm 1.8 as it would have helped a bit inside some of the mosques where there is less light but the 2.8 was still pretty adequate. I also had the 11-16mm and that could have came in handy a few times.
I guess in general if you want to pack light then a 17-55 or another midrange fast lens would be fine for pretty much anything and if you want to be covered then maybe a wide angle and a fast prime would get some use. I wouldnt bring anything on the long end as I simply never found a need for it.