Limbo means “fringe”, so it is part of another place.
The Magisterium does teach that there is a limbo of Purgatory, also called the limbo of the Fathers. This can be thought of as an upper level of purgatory where souls are no longer suffering for their sins, but are waiting for heaven. (Pope Benedict XII, On the Beatific Vision of God.)
The Magisterium also teaches that there is a limbo of Hell, a part of Hell where there is the least suffering. Souls there suffer only from the deprivation of Heaven, not any active punishments. The souls who die in original sin only go there. (Council of Lyons II, Council of Florence).
Limbo as a third final destination was a theological opinion that has fallen out of favor with most persons. The ordinary non-infallible Magisterium did at one time teach this idea (e.g. the 1949 Revised Edition of the Baltimore Catechism, n. 3). But the Magisterium no longer teaches it. The non-infallible teachings of the ordinary Magisterium are non-irreformable; they can change.
The CCC teaches that only those souls that commit an actual mortal sin and refuse to repent go to Hell. 1037 “God predestines no one to go to hell; for this, a willful turning away from God (a mortal sin) is necessary, and persistence in it until the end.”
But the Councils of Florence and Lyons II taught that persons who die in mortal sin or in ‘original sin only’ go to Hell. How can we reconcile these two teachings?
The sin of dying in ‘original sin only’ is the actual mortal sin of omission of never having found sanctifying grace in this life (baptism by water, or desire, or blood) despite ample opportunity. Prenatals, infants and young children who die without baptism do not die in original sin only. (None of the definitions of doctrine on this topic say that they do.) They receive a baptism of blood, just like the Holy Innocents, and so they die in a state of grace and go to Heaven.
If prenatals who die in the womb went to Hell, then that would be tantamount to predestination to Hell, since no baptism of water is possible in the womb. Such a claim contradicts the Magisterial teaching on the universal salvific will of God.