Vizima under a blanket of ice
As noted by Avallac'h, it is the world that's present in the time of Tedd Deireádh - Time of the End and The White Frost. Geralt has to travel through it on his journey to Tir ná Lia with the elven sage.
In The Witcher computer game
The Ice Plains is a place in Jacques' visions, to which the Grand Master teleports Geralt during the Epilogue, as part of the Frozen Reflections quest, as he attempts to convince him that what he has done is all for the greater good. Regardless of the time of day, this area is always in full daylight.