The Cenotaph in Buitenkant Street (at the bottom of Adderley) is a memorial of those who died in the World Wars, as well as for those who died in the Korean war.
The Wikipedia page quotes South Africa's 1924 Governor-General, the first Earl of Athlone as stating:
"I cannot but believe that the existence of these visible memorials, which are to be found throughout the world – silent witnesses to the desolation of the war – will through the years to come, be potent advocates of peace and will eventually serve to draw all peoples together in mutual understanding."
I can say, that looking at these memorials up close, I can see exactly what he meant. Whether they'll have any effect on war-makers; of that I'm unconvinced.
(Oh, and in case you missed that... no, neither did I know that Athlone had Earls!)