The Tongariro River Trail officially begins in the town centre at the Information Centre where you can pick up a brochure showing its route and points of interest although a good starting point on the actual track is at the end of Koura St near the Major Jones swingbridge.
To get to the cache, cross the swingbridge and turn left, (north). It's not far along this track. You could just retrace your steps if time is short, otherwise continue north up and over the hill for great views up the river, south to Mt Pihanga and north to Lake Taupo. At the northern end, the track passes under the road bridge and then after crossing the bridge, you can return via Taupehi Rd or along the riverside track through Taupehi Reserve and back to the start.
This whole 5km northern loop takes about 1 hour on foot but as a result of the track upgrade in 2013, it can also be ridden by mountain-bike. Heading north along the east side of the river as described above, the track (beyond the cache site) up and over the hill is rideable whereas in the opposite direction (uphill and south from the SH1 road bridge), the steepness of the zig-zag track makes it much more of a gut-busting ascent.
The Flying Fox: NIWA staff use this to collect water samples to test against ecological standards and suitability for swimming. Chemical and physical tests include dissolved oxygen, pH, ammonia, phosphorus, nitrogen, temperature and turbidity. On the only occasion I have seen the flying fox in use, I was told that the device they had lowered from it into various places across the river's width is used to measure water flow rate. Water diverted from the Tongariro and other rivers into the Tongariro Power Scheme is controlled to maintain at least a minimum flow rate for the ecological health of the river. With Genesis Energy now focussed more on profit for shareholders and less on the environment, independent monitoring of the river is more important than ever.
N.B. The flying fox itself and support structures are locked off and are strictly NOT accessible to the public.
The cache is a small plastic snap-lock containing just a waterproof log sheet so you'll need to BYO pen. Please use stealth to minimise attention from passing muggles (on foot or bike), especially as GZ is down a short but very visible detour off the track.