The Omdurman Souk is the largest traditional market in Sudan and, by some counts, one of the largest in Africa. It sprawls across the centre of Omdurman in a tangle of covered lanes and open courtyards, with whole quarters given over to a single trade: gold in one street, silver in another, ebony carvings, spices, leatherwork, sheepskins, ivory beads, and incense.
This is where you come for souvenirs — and for a far better atmosphere than Souq Al Arabi across the river. The silver section is particularly worth visiting; Sudanese silverwork has a long tradition, and prices are reasonable if you bargain. Avoid the heat of the middle of the day; mornings or late afternoons are best, and the souk winds down before dark.