Prince of Persia: The Forgotten Sands Walkthrough 26 - Final Climb

Stand on the switch to activate the cascades. If you don't have enough health, you can break the vases in the room, but might not be worth the time considering the difficulty of getting out of the room. Stand between the cascades and run up the one on the right. Stand bounce off and jump onto the nearby pole on the left.
Afterwards jump onto the cascades, go pass the first one, freeze time, bounce off, let the time flow and get to the terrace fragment.
You have to jump similarly between the next cascades, until you reach the switch on the upper floor.
Stand on the switch and jump between the cascades to the other side of the room.
You will have to deal with a large group of enemies. It's a great occasion to take a moment and, if you haven't before, kill 50 enemies without receiving any damage or reversing time to get [Trophy - Sand Nemesis].
Run up the cascades and start going round the room. From the stones, run behind the cascades and jump towards them. Of course you have to manipulate the time so that you go through some of them and bounce off of others.
While upstairs, use the vultures to move on.
The last stage consists of fighting the enemies and a bit of acrobatics in between sliding down ramps and grabbing vultures.
Eventually you will get to a platform on which you will fight Ratash for the last time [Trophy - Eye of the Storm]. Above all, you have to learn his movements, as it's the only way to know to which part of the platform you need to move. Attack the medallion on his chest only once he rests both his hands on the platform or hits it with one hand. In the meantime you can kill the sand monsters to regain health. Once Ratash start shooting small lighting, just run round the platform. Once he's got almost no health, he will move back. Jump towards the vulture and enjoy the ending [Trophy - End of the Army].