Jerusalem is the skull, and the going up is the whole of a life climbing toward one event that happens inside the head. The twelve are the twelve powers of the mind, every faculty gathered and turned in a single direction, because nothing scattered arrives anywhere. The skull is named here not as the ordinary seat of thinking but as the womb of a second birth. God wakes in that narrow place, is born out of your own skull, and rises.
The Son of man is the awakened being formed within a person, and everything the prophets pointed to is the account of how that one comes to term and is delivered. So the climb ends in a birth. This is the resurrection the old writings meant, not a far-off execution to fear, and not a settled mood that quietly ripens into a wish. What is accomplished is that the God asleep in a person finally awakens as that person.