Final answer:
The city that thrived under Songhai rule was Timbuktu, with Gao serving as the capital and an important center around which the empire was built.
Step-by-step explanation:
Under the Songhai rule, the city of Timbuktu really thrived particularly during the fifteenth and sixteenth centuries. As the capital of the vast Songhai Empire, Gao also played a critical role, being the epicenter around which the empire was built. The Songhai Empire, known for being one of the largest empires in African history, had its power base in Gao and saw cities like Timbuktu rise to prominence as centers for trade, education, and Islam.
The Songhai rulers capitalized on the lucrative gold trade and were notable for their ostentatious pilgrimages, following the example of Mansa Musa from the earlier Malian Empire. Timbuktu, in particular, became an important urban center known for its educational institutions. Armies of the empire possessed a cavalry of horsemen and a navy of canoes, and the economy also benefited from the work of guilds of craftsmen and slave labor.