Where is the boss key in Twilight Princess to get to Ganondorf

First, locate the outside of the castle on the side. If you want detailed directions Mr. Pushy. My directions will start when you enter the castle. Take down the enemies that come at you, then climb up the little stairway on the left and use
the claw shot on the chandelier above to reach a balcony.
Open the chest here to acquire the Compass. Then aim for the nearby chandelier and lower
yourself first, so you have a good shot at the next chandelier. Aim for
the next and land on the small balcony. Enter the room here.
Defeat the knight in this room, then go stand on the lowered tile behind
the raised one (it's actually a stairway, but it's simpler to just use
a little trick to go faster) and take out your boomerang. Aim at the torch
on the left side of the room and throw it at to take out the flame. The
step you are standing on will raise. Open the chest above to obtain a
Purple Rupee. Now you can go either right or left. It leads to the same in
the end.
East hallway: Knock down the painting on the wall with an arrow to reveal
a pattern. Light the four torches following the pattern to open the door.
Defeat the enemies in the next room to unlock the doors.

West hallway: Shoot down the middle painting on the right wall with an
arrow to reveal a switch. Shoot it to open the door. Take down the two
knights in the next room to unlock the doors.

Exit through either of the doors leading to the ramparts outside of the
castle and open the chest containing the Big Key at the end of the left
one. Have fun killing Ganondorf. And say hi to him for me. One more thing all the credit goes to ign. If you want more help with the game look on ign.com. Have fun.