How is leather tanned and dyed in Fes?

Nothing prepares you for the Chouara tannery in Fes — the largest and oldest in Morocco, worked the same way since medieval times. You climb to a balcony above it, and a shopkeeper hands you a sprig of fresh mint to hold under your nose, because the smell rising from the pits is ferocious. Below you is a vast honeycomb of stone vats — white ones on one side, a paint-box of colour on the other — with men standing waist-deep, working raw animal skin with their hands and feet. It is one of the most extraordinary sights in the country.

The process starts in the white vats, and this is the part people find hard to believe. The raw hides are soaked in a caustic mix of lime, water, salt and pigeon droppings — the ammonia in the droppings acts as a softening agent — which loosens the hair and flesh and prepares the skin to take dye. Tanners scrape the hides clean over wooden beams, then leave them to cure in this solution for days. It is brutal, ancient chemistry, and it is why the area smells the way it does.

Once softened, the hides move to the round dye pits, and this is where the colour erupts. Each pit holds a natural dye — yellow from saffron, red from poppy and the cochineal-like sources, blue from indigo, brown from henna, green from mint. The tanners climb into the pits and tread and knead the skins by foot, like pressing grapes, until the colour soaks right through. Then the dripping, brilliantly dyed hides are carried up and spread across every available rooftop to dry in the Fes sun — a patchwork of colour you can see from above.

You watch all of this from the leather shops that ring the tannery — they let you onto their terraces in exchange for a look at their goods, no obligation to buy. Go in the morning when the pits are busiest and the light is good. A two-day Fes itinerary leaves plenty of room, and our guides will steer you to a viewing terrace rather than a hard-sell room. Bring the mint; you will be glad of it.