If you came from the east, passed Russafeld Wayshrine and Rellenthil, you should head south and follow the river deeper into the territory. It will be your guide, and should help you make sense of the surroundings. Although it doesn’t seem like it, this area has a lot of wide open spaces, full of trees, boulders, and water. It would be a bit difficult to stay on track here, if it weren’t for the map.
If you’ve been following the river from the north, at one point you’ll get close to one of the hill rises. This one is a bit specific, as it has a tall tree with a Skyshard next to it. It is placed among the egg-shaped stones, next to the flower bed. A rather neat looking site right there. It gets even more astounding as you pan your view up, toward the Cey-Tarn Keep in the distance. It looks like it was built in the clouds.
Sand Kingdom Moons - Super Mario Odyssey Power Moons