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Wedged among the ancient buildings and serpentine passageways of Fez’s Old Medina in Morocco is a grid of stone wells, each filled with a colored liquid. This is Chouara, an 11^th-century tannery that still operates as it did a thousand years ago.

Cow, sheep, goat, and camel hides are brought here to be preserved, dyed, and turned into the handbags, jackets, and wallets sold in the surrounding souks.

The process begins with the raw skins being soaked in a mixture of cow urine, pigeon feces, quicklime, salt, and water—the liquid in the white wells. This loosens the hair from the hides and makes them softer. After a few days of steeping in this concoction, the skins are hauled out and hung from rails on the balconies to dry. Then comes the dyeing. Tannery workers plunge the skins into the colored wells, leaving them there for a few more days to absorb each hue. The dyes all come from natural substances, such as indigo, henna, saffron, poppies, and pomegranates.

Visitors are welcome to observe the tannery in action, and are even given a gift upon arrival: a small spring of mint to hold under the nose when the smell becomes too much.

Visit Atlas Obscura for more on the Chouara leather tannery in Fez.

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• Mosaics, storks and brothels, this ancient city has it all
• The world’s largest film studio lies in the Moroccan desert
• Just eight families now live in this spectacular ancient fortified city