Te Ara a Toa is the official name of the viaduct right next to this cache. It forms part of the Transmission Gully Motorway and is the largest structure of its type on the route. The new track that connects Takapu Road with Maara Roa goes right underneath the viaduct and the cache is near that underpass.
The curved structure of Te Ara a Toa.
The bridge while still under construction.
The bridge was constructed using the incremental launch technique from the west bank (where the cache is). The bridge is curved with a radius of 1100 metres which made that a little more difficult than usual. The deepest point in the valley is 60 metres below the bridge.
Also notable is that the bridge was designed to withstand a "1 in 2500 year" seismic event despite being a viaduct which it does by sitting on large base isolators to allow the piers to move somewhat independently of the deck when required. As you walk underneath the viaduct to this cache, the 4 isolators on the west bank are clearly visible up close. The 4 on the next pier are also visible which clearly shows the deck perched on the 4 isolation points.
4 isolators on the first proper pier.
This cache is very close to the motorway on a walkway out of view from it. You cannot access the cache from the motorway for obvious reasons but it is only a couple of minutes walk from the parking area at the end of Takapu Road. Follow the track eastward parallel to the motorway until it drops down underneath it. Since the cache is on the Belmont Park track network you can also get to it on foot from Cannon's Creek or even Lower Hutt.