I found these truly lovely images on Mashable. They are ‘colour’ photos of Rome dating from c. 1890, sourced from the Library of Congress. These were taken seventy years after Keats was in Rome, but it still feels like a glimpse into the world that he would have recognised. Joseph Severn would have known this Rome, as he died only ten or eleven years before.
I’ve copied the two most relevant images here (with great respect, but without permission) and you can see the rest via the link below.