Cavers have discovered what is believed to be New Zealand's first cave system more than 1km deep in a mountain west of Nelson.
The team of three cavers, Kieran McKay, Aaron Gillespie and Troy Watson, made the connection between two known caves in the Ellis Basin, on Mt Arthur in Kahurangi National Park.
The system went from 775m to 1026m with the discovery and is now one of the top 80 deepest caves in the world but with a bit more work it should get into the world top 10 next summer, Mr McKay told the Nelson Mail.
Until now Nettlebed Cave, also on Mt Arthur, at 889m, was New Zealand's deepest cave system. The new system is 33.4km long - making it the second longest cave in New Zealand after the Bulmer Cavern on nearby Mt Owen, which is 66km.
The cavers' gruelling journey to link up the caves in the area ended on the last day of the season during February and using the last few metres of their one kilometre worth of rope. Enduring temperatures as low as 2degC during the 10-day mission, Mr McKay said it had been generations of cavers who laid the foundation that had led to the momentous occasion.
"We finished the project but it was started in the 1960s by cavers who first explored the area and the groundwork that they laid has really helped us. Hundreds of cavers and thousands of hours have been involved in this discovery," he said.
The discovery was especially rewarding for Mr Watson, whose father was one of the original cavers to explore the system in the 1960s.
Nelson Speleological Group president Andrew Smith said local cavers did not know much about the discovery.
They were now waiting for a survey and an article in the NZ Speleological bulletin to reveal more so they could explore it themselves, he told NZPA.
The group essentially gone into a little used cave system on Mt Arthur "pushed it a bit harder, smaller, tighter" and found a way down into the larger Tomo Thyme cave system in the Ellis Basin, he said.
NZPA