The tourists are headed to the Blue Pools in droves and you shouldn't miss the pools either. But after crossing a suspension bridge, 150 meters before the pools, there is a fork in the wooden boardwalk where another trail ascends steeply. Onward intrepid runner into a world of your own! Singletrack is a misnomer; halftrack or vanishing track would be more accurate. If it weren't for the frequent orange triangles nailed to trees to mark the track, you would wonder if you were on a trail at all.
The track follows the Blue River from above at a distance of 100-1000 feet under thick forest canopy. It climbs 190 meters steeply over 0.8 km before losing most of the gain as it quickly drops to cross a forested basin of mature silver beech/tawhai. Then it climbs again, more gently, sidles up a gorge and descends to Camp Flat, a grassy knoll. This is a good lunch stop or campsite. The Blue River is easily accessible from Camp Flat but sandflies will likely deter more than a short photo opportunity. This is where the majority of folk turn around.
However, from Camp Flat it is possible to continue well into the valley. The trail follows the Blue River, crossing it several times. There are no bridges at these crossings, and if the water is high they could be dangerous. This trail is not for the faint of heart; you should know what you're doing if you opt to head this way!