Jeremiah 4:5

5. Blow ye the trumpet, etc. The invasion of a hostile army is proclaimed. The cry of alarm resounds throughout the land. The inhabitants are called to betake themselves to their cities. From the first, the most fundamental notion of a city was that of a covert from danger; a place fortified and thus protected from hostile incursions, and so supplying the conditions of possible culture and development. Thus the “city” which Cain built was simply a natural stronghold selected and built up in such a way as to become a starting point and centre of that world-culture which so eminently characterized the Cainitic race.