Owing to a long delay in the rain I have spent some time looking into this...

my thoughts are- wadi halfa (although i think the scenery is too green)
kisumu (in my mind I can imagine the shores/headlands of the lake making the required shape but I think the surrounding terrain there is probably flatter than the image
fort bell, which has some of the same issues

fort Lamy (now n’djamena in chad)- again, terrain and colouring not right IMO

thus I am stuck 😂