I lived in Christchurch so we had the Port Hills just 20 minutes from town they have some awesome tracks there, Rapaki Track was a favourite it's a 3.5 km track that climbs 250m. It's hard work getting to the top but once you're there you've got access to all the tracks along the summit.
We used to ride up Rapaki then across to the Flying Nun track which is sort of XC/beginners DH track then ride back down Rapaki.
The view from near the top of rapaki with a bit of the track on the left.
Only shot I could find on google of a section of the Flying Nun track.
There were a few nice forest XC tracks as well that were again only 20-30 min from the CBD. I definitely miss NZ for the riding.
Mates of mine were big into DH but I never had a DH bike, or balls of the requisite size.
Since moving to WA I've done a bit of riding in the Goat Farm, on the John Forrest, a few of the Kalamunda tracks, one in Jarrahdale and one near Nanga.