A visit to the tanneries was quite an experience. Walking through the medina of Fez, you will definitely be stopped by more than one or two locals begging to guide you to the tannery. I suggest finding a licensed guide before setting off to find it on your own, unless you are navigationally gifted.
After being led by our guide down the twisted and narrow paths in the Medina, we were taken up to one of the leather shops ( the best views of the tanneries working can be seen here.)
My husband and I were greeted by merchants with sprigs of mint to ward of the very strong odor that is definitely an assault on the senses. It is quite fascinating to stand upon the rooftops and watch the tanners using nothing but their bare hands and feet to dye the leather.
Leather tanneries in Morocco still follow the ancient system of treating leather. Hides are soaked for a few days in vessels full of cow urine, quicklime, water and salt before being picked at and dried. Next they are sent to a different set of vessels filled with diluted pigeon excrement and water to be softened. With nothing but their bare feet and hands, tanners knead the skins to their desired softness as well as with the final dying process.
Afterwards, you have the option of purchasing leather products in the shop. No worries, the merchants are not offended if you decide not to, just be polite when declining.
This was definitely one of the highlights of our trip to Fez.