[0]https://en.wikipedia.org/wiki/Great_Zimbabwe
[1]https://en.wikipedia.org/wiki/Axum
[2]https://en.wikipedia.org/wiki/Ashanti_Empire
[3]http://richard-hooker.com/sites/worldcultures/CIVAFRCA/SWAHI...
https://en.wikipedia.org/wiki/Ghana_Empire
https://en.wikipedia.org/wiki/Mali_Empire
https://en.wikipedia.org/wiki/Songhai_Empire
The Mali Empire was so wealthy that Musa I's pilgrimage to Mecca destabilized the gold market of the eastern Mediterranean.
Not so large, but noteworthy for the admiration Europeans showed for Benin City / Edo, and for its centuries of history of trading extensively with Europe (and even employing European mercenaries to assist in attacks on surrounding states). E.g. a Dutch account from the 17th century (from the Wikipedia link):
> The king's palace or court is a square, and is as large as the town of Haarlem and entirely surrounded by a special wall, like that which encircles the town. It is divided into many magnificent palaces, houses, and apartments of the courtiers, and comprises beautiful and long square galleries, about as large as the Exchange at Amsterdam, but one larger than another, resting on wooden pillars, from top to bottom covered with cast copper, on which are engraved the pictures of their war exploits and battles...
The "special wall" was the Benin Earthworks[1]:
> They extend for some 9,900 miles (16,000 kilometres) in all, in a mosaic of more than 500 interconnected settlement boundaries. They cover 2,510 sq. miles (6,500 square kilometres) and were all dug by the Edo people. In all, they are four times longer than the Great Wall of China, and consumed a hundred times more material than the Great Pyramid of Cheops. They took an estimated 150 million hours of digging to construct, and are perhaps the largest single archaeological phenomenon on the planet.[3]
... and it was destroyed by the British [2] as they conquered, burned and looted the city.