While running like a crazy person around (I tend to do that) I walk upon this place (sorry for low quality… phone pictures) in south east, near the Nilfgaardian border:
It looks like a semicircle of 5 altars of some sort, each altar having a symbol on him (swallow, sea monster, dog, mare, and another bird). Looks important/fun but is nothing around (they don't glow on witcher senses, can't interact with them).
From what I remember my first playthrough didn't get me here (but that was like 2+ years ago so I may be wrong) so I don't think is related to the main quest.
So… what is this place? Anything here? My guess is that is not just for flavor but…
Best Answer
According to this Reddit thread, those 5 pillars do not have any functional purpose in The Witcher 3 but serve as a reference to a quest from the first Witcher game