What is this Tunnel for?

Ben over at ben.run is intrigued by the above tun­nel, locat­ed in the Ngaio gorge val­ley…

It looks old, how­ev­er there is a pipe in it that appears to be still con­nect­ed. If there is a pipe in the tun­nel, then it must have anoth­er end, rather than just a bor­ough in the hill. So what is it for? When was it built? What is it used for now? And most impor­tant­ly, where is the oth­er end??

If you’ve got any ideas, head over to ben.run and leave a com­ment.