New caves on Mt Arthur at the top of the South Island have been discovered by accident.
A storm forced a team of cavers planning to explore the Ellis Basin system in Kahurangi National Park near Nelson to take shelter in an area on the western side the mountain.
The leader of the group, Kieran McKay, says they found a new system of caves they have named Stormy Pot.
"It's in a completely new area, quite a long way from any known caves and it's very high up the mountain.
"As far as exploration and discovering a new cave goes, it's really, really important. With a bit of luck it will connect to one of the caves lower down the mountain and we'll have a massive system."
Mr McKay says the system has big shafts and could go anywhere.