The Napier-Taihape Road
According to Google Maps the Napier-Taihape is only 134kms but it is a pretty fantastic 134kms.
Once upon a time there was a reasonably lengthy gravel section but a few years ago the sealing was finally finished. Before this I had ridden it once on my K2 Bandit which was a bit spooky as there was some fairly deep stuff in places and it wasn't a lot of fun when a loaded logging truck went past going the other way.
When I finally got a more capable gravel riding beast (my V-Strom) the road was nearly completely sealed bit I still enjoyed that last bit of gravel.
Nowadays the road is pretty good but can get a bit cut up by the big trucks and there is often metal on the road and the occasional section of hot slippery tar during summer. As the road takes you through some great scenic country you will also come across campers crawling up the hills and through the windy bits.
As you get up quite high in places and there are plenty of shady corners, snow and ice could be a problem during winter. It can also blow across the tops.
Bearing in mind the few little hazards I mentioned above I still can't recommend this ride enough. It really is bikers' heaven with corners and climbs for Africa. And it's just as good in either direction...