Possible Clues:

• Africa's second largest city
• A move to split large South African city
• Chief city of Nigeria
• Africa's most populous city (21+ million)
• Home of Nigeria's Gidi Culture Festival
• Center of the Nollywood film industry
• Africa's largest city that's not a national capital
• Strange goals of the Nigerian port
• Former African capital of 13+ million
• Trail thus coming north arriving at African city