Maybe it's "Bekle bizi İstanbul" from Edip Akbayram.

http://www.youtube.com/watch?v=WIVcknIh14w

No. Not lots of people would sing together a song by Edip Akbayram. For instance I don't like him at all.

I think the song you heard was "Bu sabah yağmur var İstanbul'da" by MFÖ.

http://www.geocities.com/duztaban2000/busabah.mp3

Thanks erdinc but that was not it. This song I speak of has a refrain in it where the singers is calling out "Istanbul" almost as if in pain, in a high pitch tone. Possibly the song of as turk living elsewhere and is no longer in Istanbul. Just a guess.
But again, thank you for trying to help me with this!

mltm,
again, thanks for trying but that was not either. I will make sure I ask the next time I hear it when I'm out.

I think its a remake of "canim istanbul" by Necip Fazil Kisakurek. Possible? I found the lyriks and I think they sound right, but I cant find the actual song anywhere.

I think it is istanbul from CEZA who is doing hiphops?

On this webpage there are six traditional İstanbul songs. Is is one of them?
http://www.istanbul.com/Kesfet.aspx#

You see here a picture that shows where to look on that page:
http://img169.imageshack.us/img169/1796/untitledpt7.jpg

I checked Necip Fazıl Kısakürek's poem and I don't know any song with these lyrics.