Complex sentence: Here, on 2 March 1800, died his wife's niece, Rose Aylmer, whose memory is perpetuated in a poem of that name by Walter Savage Landor.
Split into simpler sentences: Here, on 2 March 1800, his wife's niece, Rose Aylmer, died. Her memory is perpetuated in a poem of that name by Walter Savage Landor.