What do i do next in asins creed brotherhood?

Ok I am 30% synch. I have Revovated everything in the area. But the 2 borgia towers. Along the right side. and the one south-east are locked, and i cant go past it. It wont let me, there is a ! over there, but it wont let me past a certain point. I have bought everything in the area. And did all mission that showed, I have not bought all of the landmarks though. i also have 9 fully ranked ins. I dont know what else i can do. I bought all of leonardos things, And he said destroy the machines, im guessing they are in the area i cant go to. Any ideas on how i could get past the barrier, and do the missions, or get into trhe locked area!!!!???