The Poetry Foundation online doesn't include this title, "In the Long Hall," in its list of Donald Hall's poetry, nor is this title discussed in the article written by the Foundation about Donald Hall. The only two titles that seem even vaguely reminiscent of the title you ask about are The Town of Hill (1975) and Great Day in the Cow's House (1984). Are either of these what you are asking about?
I have been unable to find this exact poem, but from my research it seems that Donald Hall really likes to use metaphors in his poetry. Metaphors are comparisons of two unlike things. We make these comparisons so we can see the common truth in both.