Take a flight to thunder bluff, goto sprit rise and behind thetent you will see the fire.21.26

When you stolen all four cities of the opposite factions flames, and completed the quests of returning them, you unlock a final quest for a new hat.

Here are the quests.

https://vanillawowdb.com/?quest=9365 Alliance

https://vanillawowdb.com/?quest=9339 Horde

Just a tip, this is a very good place to do the torch catching daily. The limited area means you won't have to follow the shadow of your torch quite as far, and the light color of the ground makes it much more visible than the shadows of torches thrown in Undercity.