The Macquarie Pass in New South Wales is one of the first routes found up onto the colossal escarpment west of the coastal plain. This features in the final book in the series, Volume 5 'Crossing the Rubicon'.
'The combat team’s available manpower was sent down onto the plain behind the town where JCBs from the plant hire depot joined them in creating fighting positions there. Heck and Tony McMarn then travelled west along the Illawarra Highway to the Macquarie Pass. The Pass led the way through the escarpment and on to Canberra a hundred miles beyond, an obvious target for any invader. One other road led through the same gap, the Jamberoo Mountain Road, looping around from the south to join the Highway at the top of the Macquarie. Heck found a good piece of ground to defend, one that dominated both the pass and the mountain road. This was the men’s and the JCB digger’s next task.