The western Sudan is crisscrossed with trade routes linking this interior region of West Africa to the Atlantic coast and ultimately to cities across the Sahara. The western Sudan is the first area of sub-Saharan Africa to be reached by Muslim traders, and the influx of wealth, goods, and cultural and religious influences contributes to the dynamic artistic production. Nok, in the eastern part of the region, is one of the earliest African centers of ironworking and terracotta figure production. Jenne-jeno, populated as early as 250 B.C., is the oldest known city of sub-Saharan Africa. By 850 A.D., it has become a major urban center but is just one of at least twelve sites of comparable size in the middle Niger region. Several other significant political and commercial centers emerge during this period, including Timbuktu, an important site of Islamic religion and scholarship as well as trade.