I found an interesting area, hidden on the slope of the plateau that overlooks Pontar (near the nest of the royal wyvern from Phantom of the Trade Route contract).
Not sure yet what that is. Looks like some ancient ruin, with circular ledge carved into the mountain with cobblestone ornaments. It's pretty hard to notice, unless you try climb on the mountain from the river side (which I was doing for fun and saw that structure). But you can't get to it climbing up, you need to get down to it from the top of the plateau.
View from the top:
When entering the stone circle:
Looks like some kind of altar with some statues around it, probably to Melitele?
Magnificent view of the Pontar from there
I suppose it could be a part of some quest, or may be just one of those hidden ruins that are scattered around. Interesting to discover such places sometimes
UPDATE: There is also an entrance to the cave, which is actually connected to the cave where refugees were hiding from the wyvern, with another unmarked cave exit leading straight to the wyvern nest (I missed that cave entrance before).
UPDATE2: Yep, the statue looks like one of young Melitele in
St. Lebioda's Hospital hospital in Vizima.