it was n't the dark tower , not his dark tower , at least ( although it would n't have surprised him to know there were people working in yon sky-tower-some of them readers of roland 's adventures-who called 2 hammarskjold plaza exactly that ) , but he had no doubt that it was the tower 's representative in this keystone world , just as the rose represented a field filled with them ; the field he had seen in so many dreams .