This is wide river valley on the edge of Arthurs Pass National Park and is a trial by DOC to see how mountain biking goes within a national park. The ride starts from the Mt White road and drops down into the valley.
The track then generally follows the river up the valley on a well formed 4WD track.
This track eventually runs out and you can either turn back at this point or as I did carry the bike for about 2km to the Poulter hut for a nights stay and explore the area.
There is a small amount of singetrack past the hut heading up to Lake Michin pictured below but probably better to walk I think.
Here’s a map…