Why does birdy compare aelis castle finbury to a stone city?

Birdy compares Aelis Castle Finbury to a stone city to emphasize its strength, permanence, and the emotional weight it carries. The imagery of a stone city evokes feelings of resilience and tradition, contrasting with the fragility of human experiences. This comparison highlights the castle's role as a steadfast presence in the characters' lives, reflecting their struggles and aspirations. Ultimately, it serves to underscore the themes of stability and change within the narrative.