How is the Wood between the Worlds like the tunnel in the attic?

Think of our tunnel under the slates at home. It isn't a room in any of the houses. In a way, it isn't really part of any of the houses. But once you're in the tunnel you can go along it and come into any of the houses in the row. Mightn't this wood be the same? - a place that isn't in any of the worlds, but once you've found that place you can get into them all."

The similarity between the two places gives the boy a wild idea. What is it?

Now that they are in The Wood between the Worlds, Digory wanted to explore other pools to see where they can get and go adventure.