Don Bosco dream and/or vision.

Granted that St. Don Bosco dreams are private revelation, but there is one dream in which he witnesses St. Dominic Savio playing with some other children. He assumed he was in Heaven, but St. Dominic Savio corrected him - they were in limbo.

Perfect natural happiness and yet it paled compared to the sliver of Heaven that he was allowed to see.

[...]
"Where am I?" I asked.

"You are in a place of happiness," he replied, "where all is beautiful can be enjoyed."

"Is this Heaven, then?"

"No, whatever is here is of the earth, although improved beyond conception by the power of God. No living person can ever see or imagine the wonders of eternity."

"Would it be possible to have natural light more brilliant than this?"

"Yes, quite possible . . . look there in the distance."

I looked, and a ray of light suddenly appeared, so penetrating and of such brilliance that I had to close my eyes, and I cried out in alarm so loudly that I woke the priest who was sleeping in the room nearby. I opened my eyes after a moment and said:

"But that is surely a ray of divine light . . ."

"No even that does not give you any idea. In Heaven we enjoy God, and that in everything." [...]