Homosexuality - while not actively condoned - is also not actively shunned in Turkey, a tribute to it’s efforts to adopt more progressive western notions of human rights.  As such, the gay scene in Istanbul is extensive and deserves several nights of focused effort to make sure you see the wide array of venues and cliental.  While there is no distinct “gayborhood,”  most gay venues are clustered in the Taksim and Beyoglu neighborhoods.