After you reach Rito Village in the Hebra region, you meet Tulin and learn of the Stormwind Ark.
After you talk to Tulin, Teba, and Saki, you can jump and glide from the landing toward the stone column in the direction of the two bonfires that Teba pointed out. Climb to the top of the column, then glide from there to the area with the bonfires, but be careful of the Ice Wizzrobe.
You will find Nekk standing near the two bonfires. He points out the location of the Skyview Tower.
Go into the lodge and talk to Harth. He tells you to look for Tulin at Hebra South Summit Cave.
Go outside and go up the ladders that Harth showed you. Make your way up the slope and you will find Cecili at a campfire. She will show you the way to the cave.
Before you go, look southwest for the Skyview Tower. You can go in that direction from here to reach it. It is called the Rospro Pass Skyview Tower.
Go back to where you were and go east up the slope. Look to the west for a bonfire in a cave opening. Go in to find Hebra South Summit Cave.