The upper Mangatoetoenui valley has a remote, rugged character, dominated by the peak of Te Heu Heu. Two lines of bluffs exist on the true right of the river. The upper tier is steeper, very compact and brittle-looking. The lower series, which (counter-intuitively) runs further up the valley, is somewhat similar in composition to Whakapapa Gorge: reddish in colour, iron-hard and with good natural protection. There is scope for many more routes, mostly at moderate grades.
A waterfall makes direct access from below difficult; the best route in is via Tukino skifield. From a point about half way up the top rope tow, turn right (north) and up across the broad ridge. Pick a route down into the upper valley; be aware that a line of cliffs can cause problems. There are cairns on some alternative routes depending on which wall you are heading for and the access points to descent gullies and ledges are cairned.
Thanks for proofing and correcting Richard.