If you mean the reasoning for it being built, it was built to keep refugees from leaving East Berlin.
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The relationship Katniss and Gale have in the book the Hunger Games by Suzanne Collins is a very trustworthy friendship. Katniss says when asked "who would be your best friend" she straight away says Gale meaning they share a close connection with each other. ... Gale says I never smile except in the woods."
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