The skyshard you are out for is inside the southern part of the ruins. This is one of the most unique surroundings found in the dungeon. What makes it unique is the view from near the shard. A perfect place to make several screenshots.
Klathzgar entrance is off the road near the Old Tower.
dungeon entrance map
In southern part of the ruins.
Sand Kingdom Moons - Super Mario Odyssey Power Moons