The Hidden Blade Assassin's Creed in Depth

I haven't yet been up there myself but saw this procedure on GameFAQs:

• Enter through the south bridge... South being the bottom one, not the side.
• Go left until you see an opening on your right, just before the second bridge.
• Stay against the right wall.
• Ladder, climb it, run up the wall, kill the guard.
• Go right until it end, right again, up the wall.
• After you get up, go to the inner edge and drop down onto the roof.
• Air assassinate the guard.
• This should look familiar.
• Free run the same way as earlier in the game: Up the wooden boxes, a few leaps to a scaffold, a few more to a lower scaffold.
• Run up the wall, hand until the guard gets there.
• Ledge assassinate.
• Up to the higher roof, take care of the guard.
• Across the rope, up the wall, left, up, right, jump to the beam.
• You should now be on the main part of the castle.
• Make the jumps, up the wall, reach the window where the cutscene happened before.
• Continue as before... This beam's really far! Jump and grasp, fall, grasp the lower one, up the wall and to the right!
• Down... Right... Up... Another window that has a cutscene!
• Keep going up.
• As soon as you reach the top, go to the right and up the wall.
• One guard, do as you like.
• Up the wall on your left, three guards, take care of them.
• Continue forward, up the wall, one guard.
• Kill him, there's the flag pole.
• Climb it, climb leap works fastest.

I found a spot where you can parachute to a ledge you're not suppose to be able to grab.