Native African fortifications?

[Belgian]

Hi, has somebody pictures of drawings of native African fortifications? I'm really curious after reading these texts on wikipedia.

"Angolan armies at times made extensive use of fortifications. In a 1585 campaign against the Portuguese, the Ndongo for example constructed palisaded camps, each a day's journey apart. Use of strong defensive positions on hilltops or in forests was also common, as was the use of fortifications in offensive maneuvers. The Imbangala for example usually built a strong fort in enemy territory to bait opponents into exhausting their strength against it. Some of these positions could be quite formidable, with trenches, parapets, hidden roads, sharpened "punji" stake traps, mutually supporting bulwarks, and covered trenches to protect against artillery."

"Fortifications were important in the region and numerous military campaigns fought by Benin's soldiers revolved around sieges. As noted above, Benin's military earthworks are the largest of such structures in the world, and Benin's rivals also built extensively. Barring a successful assault, most sieges were resolved by a strategy of attrition, slowly cutting off and starving out the enemy fortification until it capitulated. On occasion however, European mercenaries were called on to aid with these sieges. In 1603-04 for example, European cannon helped batter and destroy the gates of a town near present-day Lagos, allowing 10,000 warriors of Benin to enter and conquer it. In payment the Europeans received one woman captive each and bundles of pepper."

http://en.wikipedia.org/wiki/African_military_systems_to_1800#The_infantry_kingdoms

Greets and thanks in advance!