I'd originally planned to place a cache at this location for quite a while before getting around to doing it. However the first attempt (from SH 32) was a failure after I didn't read the online description of a trip through the area by the Auckland Baptist Tramping club carefully enough. That meant we ended up going to the wrong end of the track, but I didn't realise my error until after returning home. Severe loss of brownie points with the rest of the family!
Second time around I was better prepared, having found some useful Department of Conservation information. That PDF is apparently no long published by DOC but their current information is available on this page. You can also still find a copy of the original brochure on the "Wayback Machine", and that has more detail. We entered the forest from SH 30 at Pureora which is also where DOC have a small visitor centre, walks, viewing platforms and so on.
You can drive all the way to this cache except for a walk of a couple of hundred metres at the end, but the roads are a little rough in places. The difficulty and terrain ratings really reflect that, and the rather remote location rather than the actual cache surrounds.
The original container was a small (500 ml) plastic container with a screw top lid, and so there was only room for a few small items apart from the log book and pencil. This was hidden in the clearing at the end of road, about 15 metres NE of the centre, on the ground by a small shrub. This appears to have been lost or removed by July 2004 but please let me know if you do find it!
A replacement cache is hidden very near the official geographic centre of the North Island, which is marked by a small obelisk with plaques giving a brief description of how the location of the spot was determined. This apparently involved cutting out a roughly 1 metre long map of the N.I., bending it to reflect the curvature of the earth, and then hanging it from a thread to find the point of balance. Back in 1961 this was probably the state of the art! It would be interesting to redo the calculation using digitised maps to see how accurate the old method was. Any takers?!
[Update: 13 Oct 2007. Actually I did do some double checks of the accuracy of this location back in 2002. Using 500 metre resolution DEM data that was freely available at that time, I calculated the centre of the North Island to be at about S38°32.885' E175°41.280'. This is only a couple of kilometres from the cache and obelisk. More details in this thread.]
Don't forget to check your spare tyre and fuel before leaving civilisation! We had a puncture as we pulled up in the carpark when it was first placed, and had another puncture shortly after leaving the area after placing the replacement cache! It'd be a long walk back if your wheels let you down.
This video gives an idea of the area, plus the possible side trip to the top of Titiraupenga, complete with demonstration of several potential hazards. :-)