Commentary Par XXVII 86

It is nearly certainly hazardous to translate aiuola (little patch of earth) as 'threshing-floor'; see C.Par.XXII.151. Boyle (Boyl.2000.1) is among the many who simply assume that it is what is meant by the word.

For the twin problems, exactly how far Dante had moved with the heavens and, consequently, how much of our globe he was able to observe, see Carroll (DDP Carroll.Par.XXII.151-154). His hypothesis is that the reader is supposed to identify each of the three apostles with whom Dante has conversed as having been particularly identified with efforts located in specific parts of the Mediterranean world, John with Asia Minor, Peter with Rome, and James with Spain. And thus, with regard to the second question, the protagonist's vision of earth coincides with those regions.