The seven layers of hell?

Shaw sends a link to a glimpse of an old Hebraic tradition about hell. We'll find, by the way, that Milton was very conscious of the numerological significance of the number seven:

 In many religions, the souls of the dead have been conceived of, after leaving the body, as proceeding to an underworld located below or inside the earth. In the Judaism and Christianity of classical antiquity and the medieval period, this underworld was thought to be a hellish place, called Gehinom in Hebrew and Infernus in Latin, where sinners were punished just as the righteous were rewarded in heaven. Since the universe was pictured as symmetrical, hell was heaven’s physical as well as religious opposite — and just as the heavens were pictured not as a single celestial realm but as a layering of realm upon realm, so hell was considered to have an equal number of layers descending into the bowels of the earth.

In ancient rabbinic Judaism, which could cite in its support the biblical phrase ha-shamayim u/shmey ha-shamayim, “the heaven and the heavens of the heaven,” these layers were thought to be seven — a number whose sacred status goes back to the Bible, too. (Think of the seven days of creation, the seventh or Sabbath day, the seven branches of the menorah, etc.) Most likely, this sacredness was linked from the outset to the concept of a sevenfold heaven, which in turn derived from the seven brightest and most independent heavenly bodies: the sun, moon and five visible planets — Mercury, Venus, Mars, Jupiter and Saturn. Each of the heavens associated with one of these bodies had its own name in rabbinic literature, as did each of the seven hells. The latter were, using synonyms for the underworld taken from the Bible: She’ol, Avadon, Gehinom, Duma, Tsalmavet, Eretz-Taḥtit and Eretz-Neshi’h.