Though it may seem bewildering or even exotic to outsiders, Istanbul’s commercial life is actually organized according to a very old, guildlike system that assigns different neighborhoods to the sale and sometimes manufacture of different types of products. If you bottom out in a pothole and need a rot balans, you head up to the Oto Sanayi area. For kitchen and bathroom accessories, the Çağlayan neighborhood is the answer. And when Istanbulites hanker for grilled sweetbreads, or uykuluk, the only suitable place to go is Sütlüce, down where the slaughterhouses used to operate on the Golden Horn.