From the dock: Take the middle path north of Karnor's Castle up into the mountains. You will pass through giants and then Yeti. You do not need to enter any of the caves. Instead, continue north past the caves and a bit east and follow the trail straight down out of the mountains (and the snow) and you will see a large gorge called the Gash of T'Thelin. Stay on the top, left edge of the gorge. You are almost there when you see the large hollow tree spanning the gorge on your right. Do not cross, but continue past the fallen tree for a short distance and you will find Highton.
From Teren's Grasp: Take the tunnel that is just outside and to the North of the large ramp entrance. Once through the tunnel, turn left and follow the path straight down out of the mountains (and the snow) and you will see a large gorge called the Gash of T'Thelin. Stay on the top, left edge of the gorge. You are almost there when you see the large hollow tree spanning the gorge on your right. Do not cross, but continue past the fallen tree for a short distance and you will find Highton.