Tongariro Alpine Crossing
Ok, so we didn't actually drive it, but we ate lunch in the car park at the end, and about 10-12 cars came down or went up.
The volcano in question is quietly emitting steam from its sleeping flanks, so it's not cold yet.
This is from the west, the eastern flank (at the same distance) is described as the 'desert road' as plants have not yet colonised the last eruption in 2012, on 6 August and on 21 November. Also on 14 October, there was a small lahar/debris flow from near the eruption site down to State Highway 46.
We were on Highway 47!