First you have to get to to the weird vertical platfrom, you have to jump on to the side of it, that will act as a ladder, walk up it until you get to the ledge, walk along the ledge until you get to the platfrom.

Jump on the handrail, then jump again and you get on a thin rail, walk along and you get there, the funny thing is there are loads of random teddy bears on the ground.

PS: Take a sniper up there!