The covered market at the heart of Keren is the kind of place that rewards slow wandering. The stalls are organized loosely by type — copper goods and metalwork in one section, woven baskets and mats in another, then spices and incense and dried goods — and the covered sections keep the worst of the midday heat at bay. Prices are negotiable in the way that suggests negotiation is expected, not optional.
Copper work is a Keren specialty worth looking for specifically. The local craft tradition produces bowls, trays, and decorative items that make better souvenirs than most things sold in Eritrea's tourist shops, and here you're buying from the people who made or traded them directly. Incense is another good purchase — Eritrean incense is distinctive, and the market carries varieties you won't find outside the region.