Would you say that High Heart is a possible “thin place”, knowing what happened their? “When [the Singers] died, they went into the wood, into leaf and limb and root, and the trees remembered.” (DwD Bran III). RSAFan

Maybe a mini-one? After all, that is where Erreg became known as a kinslayer, so something had to go down there. 

The thing about thin places is that it’s not just a place of supernatural power, it’s a concentration of human suffering. Hence why I would say that a place like Winterfell is NOT a thin place. Nor is the Isle of Faces, or similar places. They are places of power yes, but that power derives from sources other than human suffering.