In “To Da-duh in Memoriam” what “borders” does the narrator cross when she visits her grandmother?

The narrator crosses a geographical border first: she travels from Brooklyn to Barbados to visit Da-duh, her grandmother. During the visit, the narrator also crosses several other "borders."
She temporarily leaves her urban, modern life for a rustic, pastoral one. The narrator also begins to view life through a mature, adult lens, as opposed to her own youthful one. The journey is not only physical but also philosophical in nature. Essentially, she crosses the border from youth to maturity and from modernity to sustainability.
The narrator's modern world is replete with skyscrapers, imposing man-made structures, and technological advancements in every form. She crosses over into a pastoral setting, where the flora and fauna are sustained by the laws of nature. Da-duh introduces her to strange fruits such as papaws, guavas, sugar apples, and breadfruit. The narrator sees fields of cane and clusters of banana plants. In nature, the "tangled foliage" are locked in an "immemorial struggle" for sunlight. There is violence in the struggle; yet, the result is beauty, life, and peace. 
The narrator learns that there are differences between her world and her grandmother's. During her stay, she learns to appreciate the advantages both worlds can offer her.