At this location there once stood a maternity hospital. It was the first such hospital in Christchurch, and part of a nationwide movement towards dedicated maternity hospitals at the time of the RJ Seddon Government. It was the fore-runner of the present Christchurch Women's Hospital, and the old plaque of St Helen's was visible behind CWH (until the present major construction began and put the area out of bounds).
See http://my.christchurchcitylibraries.com/st-helens-hospital-sydenham/
It was at this hospital that my grandmother was born in 1909. Unfortunately the building was long ago knocked down. This is now a light industrial part of town.
The cache is a small camo'd screw cap container (push down and turn to open). Should not be difficult to find. Please be very careful due to high muggle count. This area of town is very busy during work hours, and parking is very difficult. More suited to weekends and after hours caching expeditions.