Stock photography, photos: Gbollu Defense Wall - Ghana Stock photos of The Gbollu Defense Wall in the Upper West Region of Ghana, West Africa. During the 18th and 19th centuries, slave raiders frequently invaded Ghana from the north. These earth barrieors were one means of stemming the onslaught of slave raiders. Photograph: © Robert Burch Click for a larger image and more information Keywords associated with this stock photo: Ghana, Africa, west Africa, upper west region, upper west, defense wall, raiders, slave raiders, slaves, invasion, defense, gbollu, slavery