I think that throughout Africa, all of the colonial construction was beautiful in its own right. There is literally nothing that the locals can lay claim to.The first time I went to Nigeria (early 2000s) I had an ex SSS guy as the local security manager. He recounted how some British bloke had a mother who had lived in PH in the '60s and asked him if he could arrange a tour for her.
According to the Nigerian manager he picked her up at the airport, and when they got to the shit hole the city had become she burst into tears. In its day PH was reckoned to be beautiful - not many who would say that any more.
The Portuguese buildings in Angola are a great example. Utterly stunning forts and ancillary constructions, only recently being restored. If you get a chance to do Luanda, I thoroughly recommend their fort reconstruction and museum. Take a local if your don't speak Portuguese.