Cities of the mountain and cities of the plain (Jeremiah 33:13) signify doctrines of charity and faith.

(References: Arcana Coelestia 2418)

4413. The fact that the light of heaven holds intelligence and wisdom within it, and the Lord's gift of intelligence, which essentially is truth, and of wisdom, which essentially is good, are seen by angels' eyes as light, I have been given to know through actual experience. I was raised up into light which was flashing like the sparkling light of diamonds. While I was kept in this light it seemed to me that I was taken away from bodily ideas to spiritual ones, and so to matters belonging to an intelligent understanding of what was true and good. Ideas present in my thinking which had been formed in the light of the world seemed at that time to have been removed from me and so to speak no longer belonged to me, although they were vaguely present. From this I was given to know that insofar as a person enters the light of heaven he enters intelligence. This explains why the more intelligent the angels are, the greater and brighter is the light in which they dwell.