the excact area is called mushroom rock precipice, it just down from where the machina is to get you up to the command centre for the first real fight scene with sin the object next to tidus id Auron Sphere part of the jecht sphere's set you have to collect to get aurons overdrives its also just down from a save point and you get to it by using those silly lifts after a long winding road!!!
that enough info???