It's a forest south of Ding Dong Dell, but it's also not accessible until after you've beaten the final boss and loaded a clear save file. You have to walk there, as Tengri can't land anywhere nearby. There's a narrow passage through the rockface south of the town that you have to work your way through.
I had an issue finding this place as well. Thing is, this place still may not be available to you if you have not done the very last "I dropped my journal somewhere" mission. You find the man one more time in Ding Dong Dell and he asks you to venture there and find it yet again. This is where The Conductor is and the entrance to fight The Defender of Worlds . Although, you don't have access to him just yet. Not until you complete some missions for The Conductor.