Calabashes on sale beside the river Niger at Mopti, once one of the major entrepots of the trans-Saharan trade caravans, The trade routes converging on the Niger bend were the heart of the great medieval empires of Mali and Songhai. Towns such as Mopti and Timbuktu became centres of trade, industry and Islamic learning. Mali. Islamic. late 1950's - early 1960's. Mopti, Niger bend.