Final answer:
Gao was the capital of the Songhai Empire, which became prosperous through trans-Saharan trade and was ultimately defeated by Moroccan forces in the late 16th century.
Step-by-step explanation:
The capital and important trading center of the Songhai Empire was Gao. The Songhai Empire, which arose from the declining Mali Empire, was well-known for its wealth that stemmed from the trans-Saharan trade, especially in gold, salt, and kola nuts. It reached its zenith during the reign of Askia the Great, whose policies fostered an era of economic prosperity and cultural renaissance in West Africa. The imperial city of Gao, situated along the Niger River, played a crucial role in the empire's economy, and at its height, the Songhai Empire was one of the largest empires in African history. Although it prospered through trade, the Songhai Empire met its end in the late 16th century when it was invaded by Moroccan forces.