One of the main themes Cushman chooses to use in this novel is freedom, though some may argue that it is obedience. This thought is not true, considering the fact that Catherine was never once obedient to her father. Cushman illustrates this theme using Catherine's birds.
C: sec 10: i have always been regretting that I was not as wise as the day I was born
The Great Wall of China is an example of a wall used to protect a place.
The Berlin Wall is an example of a wall to keep two places separate, east and west Germany.