This is a large horn in the valley of spears. Requires the https://vanillawowdb.com/?item=6074 War Horn Mouthpiece . The Mouthpiece is part of the last quest in the chain: https://vanillawowdb.com/?quest=1380 Khan Hratha . You have to go up a path and cross this bridge type rock structure to get to the horn. There are 5 different Maraudin Centaur on the way up the path you will have to fight. I tried showing the Bridge as much as possible.The Coords are 29, 53 as unitepunx stated above.

I had to give up on Loremaster of Kalimdor the night before The Shattering, and I was standing close to this.
The next day, I noticed I had lost the quest (The ramp up to the horn was destroyed), but also that they forgot to remove this object! It might still be there nowadays - totally useless.