Mysterious tunnels under posh NZ suburb
It's a tale that has all the elements of a great mystery – claims of concealed treasures and buried dangers.
For years there have been rumours about what is possibly hidden in tunnels beneath the old North Head military base in Auckland.
Various official enquiries have found nothing, but now one investigator believes he's uncovered explosive new evidence.
One theory is that parts of the first Boeing aircraft ever made were packaged up there. They were brought by the New Zealand Flying School during World War I and it's what happened to them after that school closed that has been the matter of some debate.
The second theory, which is perhaps more concerning is that there are hidden ammunition dumps contained under North Head.
Martin Butler has spent decades searching the site, which is honeycombed with gun pits and open tunnels.
He's an amateur investigator who got interested in the mystery, but, just to be clear, he says he's not a conspiracy theorist.
Three years ago Mr Butler employed a top geophysicist to scan the site with ground-penetrating radar, to find see if they could find any undergrounds spaces.
At many locations they found what could be underground structures that are not officially known to exist. These could also be naturally occurring spaces, and the ground radar also can't prove whether there are bombs or Boeings underneath the surface.
But the North Head riddle will have another chapter, with the military now examining Mr Butler's ground radar findings.
"If there's no ammo, that's fantastic. If there are no planes, that's sad, and if there are no sealed tunnels I would be very surprised."
Watch the video for the full Story report.