Adam Clarke on Deuteronomy 32:22

The lowest hell - שאול תחתית sheol tachtith, the very deepest destruction; a total extermination, so that the earth - their land, and its increase, and all their property, should be seized; and the foundations of their mountains - their strongest fortresses, should be razed to the ground. All this was fulfilled in a most remarkable manner in the last destruction of Jerusalem by the Romans, so that of the fortifications of that city not one stone was left on another. See the notes on Matthew 24 (note).