There is several kilometres of interesting singletrack in the pine forest on Blue Spur Ridge near Hokitika. One of them even goes through a short historic tunnel from gold mining days last century! You need advanced skills to enjoy these trails.
A rough gravel road called "Forest Road" is the main access to the singletrack. It climbs, steeply in places, up the ridge. Most of the singletrack trails run parallel to it and are typically benched into the side of the ridge as they traverse the pine forest. As you go up or down the road you'll see signs for the trails.
The first one to try is "Seesaw" which features some steep down-slope riding with exposure and - you guessed it - a seesaw! Turn right at the bottom for a long grind with stream crossings up a valley to the top of Forest Road. You take in several trails as you go back down Forest Road heading west- all sign posted. Slow Girl is best ridden west to east so go past it's first sign and enter at the second sign - the western end.
Next up is the Tunnels Track which is the best trail on the ridge and the most challenging. Apart from the tunnel it features some steep down-sloping rock garden action. Take three right turns on the roads back to Station Inn once you exit the Tunnels Track.