The Chouara Tannery is one of three tanneries in Fes, located in the Fes Medina along the river and near the
Madrasa al-Saffarin. The tannery has been operating at that site since early in the history of Fes, and today
operates in much the same fashion as it did in its early centuries. The site is a grid of round stone wells, some filled with white liquid (a mixture of cow urine, pigeon feces, quicklime, salt, and water used for softening the raw hides), and some filled with dye. Hides are brought to the tannery to be processed and turned into leather goods sold in the surrounding souks and exported around the world. It is also a significant tourist attraction in Fes.
Sources:
"Aziza Chaouni: Hybrid Urban Sutures: Filling in the Gaps in the Medina of Fez." Archit 96 no. 1 (2007): 58-63.
Holliday, Jane. Morocco, 155. New York : Norton, 1992.
Morton, Ella. "Chouara: A Striking 11th-Century Tannery in Morocco." October 20, 2014, accessed October 31, 2014.
http://www.slate.com/blogs/atlas_obscura/2014/10/20/chouara_tannery_in_fez_morocco.html.