I'm no expert in architecture, but I'd be fascinated to read your comparisons nonetheless.

[ Sister Imperator nodded. She herself could not see her profession ever being a prison, but she realized that there was indeed something that would, perhaps, qualify. Paul's marriage to Chani had been what had given him joy, but in Sister Imperator's case, her own union was not quite as liberating. It had been, at first, but that had quickly gone sour.

But she turned her thoughts away from Papa Nihil. She didn't want to dwell on him when she had an esteemed guest and friend visiting. ]

It is just a reminder that the end of the book is not necessarily the end of the story.