The Henna Souk is a small, pleasant square near Place Nejjarine where vendors sell traditional cosmetics and medicines: powdered henna, kohl, argan oil, oud resin, dried flowers used in Moroccan medicine, and the black antimony that Fassi women use as eyeliner. The pace is lower-key than the main souk thoroughfares, and the products are genuinely local rather than made-for-tourist.
The square also has a mulberry tree and usually a few women offering henna hand painting for tourists, which is negotiated openly (agree on the price and design before you sit down). It is a good place to buy small, light, and authentic gifts: a cone of henna powder, a small pot of argan oil, or a bag of kif-smelling herbs. Prices are reasonable if you are willing to haggle politely.