Another interesting side-note by Dr Papandrea regarding Revelation, he notes that the number 4 carries with it the sense of spatial, geometric wholeness, so that four corners of the earth = whole earth/land; four living beings covered in eyes = God’s omniscience seeing every part of the earth/land etc.
So, when he talks about the New Jerusalem being a square/cube and having four walls there is an implication that it encompasses the whole world. In a footnote Panadrea makes an interesting reference:
‘Many early christian writers interpreted the three gates as a reference to the Trinity, the idea being that that divine can be accessed by any one of the three persons of the Trinity. Apringius of Beja said that the three gates on each of the four sides predicted that the whole world would accept the Trinity, Tractate on the Apocalypse 21.13.’