NZ is probably the flattest golf course I have played. There are perhaps 3-4 holes with more than 1m of elevation change. It really is VERY flat.
But the brilliant bunkering (especially those that seem small until you get to them [2, 11, 14], those set in the middle of the front of greens [8, 14] and those that create distance perception issues [2, 4, 7]), combined with how brilliantly the small amount of elevation change (8, 13, 14) and small swales in the land (6, 12, 18) are used are what causes it to soar.
It also has an extremely varied set of par threes.
As an example of how great design can overcome site limitations, NZ has to be a poster child.
I have played many higher rated courses in GB&I, but few that I start thinking about more often in idle moments.