"cities great and fortified in heaven": R. Shimon b. Gamliel says: Scripture (here) speaks hyperbolically, as it does in (Ibid. 9:1) "Hear, O Israel, you are crossing over the Jordan this day." But when the Holy One Blessed be He says to our father Abraham (Bereshith 26:4) "And I will multiply your seed as the stars of heaven," and (Ibid. 13:16) "I will make your seed as the dust of the earth, so that if a man can number the dust of the earth, so will your seed be numbered" — this is not hyperbole. (Devarim, Ibid.)