A group of Kiwi explorers are embarking on a remarkable journey to find what could be the longest cave in the Southern Hemisphere.
It's an expedition that will take Kieran McKay and his caving-mad friends deep underground near the summit of Mt Owen in the Kahurangi National Park near Nelson.
It is thought the vertical caves could link up to a master cave measuring up to 200 kilometres in length.
More than 900 kilograms of food and equipment is being loaded for the expedition – enough to last 21 days in what can be a gruelling environment.
Mr McKay made headlines last year for helping discover the deepest cave system in the Southern Hemisphere, in the same park.
Story was with the team as they set off on their journey.
Watch the video for the full Story report.
