Most of the places we went in Mali, including Bamako, are on or near the Niger River, which starts in Guinea, flows through much of Mali and a corner of Niger before becoming a delta in Nigeria. Bamako was the furthest upstream, and we just progressed further downstream as the trip went on. This monument near the river is the Tower of Africa, said to represent a baobab tree. Here's an interesting article about this and other monuments in Bamako.