Complex sentence: The Prestor John Memorial is a Coptic Cross with two figures sitting inside it, and commemorates the Portuguese explorers who discovered South Africa as well as the story of a far older mythical figure named Prestor John.
Split into simpler sentences: The Prestor John Memorial is a Coptic Cross with two figures inside it. It commemorates the Portuguese explorers who discovered South Africa as well as the story of a far older mythical figure named Prestor John.