Answer:
Dream
Step-by-step explanation:
The "it" in the line above, is referring to the dream the writer had. Although it had been quite a long time since he had the dream, and he had even nearly forgotten, but still, the dream was right in front of him, shinning bright like a sun. A wall then rose up between the writer, and his dream.
The speaker is recalling a dream he had a long time ago, one that he had nearly forgotten, but at that might, he could see it ahead of him once more.