What of the Limbo of the Fathers, that is, that region of hell where the righteous went before Our Lord's sacrifice? Presumably, that region is now either entirely empty, or has been destroyed. When it did have the Old Testament fathers in it, was there any suffering, or was it a place of "natural happiness," where they awaited the coming of Christ?
According to the Catholic Encyclopedia, in the Old Testament the Limbo of the Fathers was a place in which the departed just enjoyed a state of "natural" happiness, was temporary, and was to be replaced by "a condition of final and permanent bliss when the Messianic Kingdom is established", meaning when Jesus Christ Our Lord opened Heaven for the human race, after
He descended into Hell.
There is no such hope of "replacement" in the Limbo of the Children, though. There is no promise of Heaven for such souls under the New Law of salvation. It is generally believed and taught by the Church that the unbaptized infants in Limbo are deprived of the Beatific Vision and the Eternal Bliss of Heaven, but their suffering is minimal, if any, and they do not receive the punishment of the senses.