Organisers describe the Northburn 100 mountain run, near Cromwell, as "brutal".
"There's no other words for it. This race is bloody tough ... brutal, even," says ultra-marathon runner Lisa Tamati, who designed the 160km course on Northburn Station.
"It's equivalent to going from sea level to the top of Mt Everest, as far as ascent goes; very difficult terrain in places and there's the occasional part dotted through it that people will be on all fours to negotiate," she said.
The inaugural Northburn run begins at 6am today and is the only off-road 160km event in the country.
Among the field are 11 international competitors.
A 100km and 50km race being held at the same time and same location have each attracted 10 runners.
Tamati and Northburn Station owner Tom Pinckney joined forces with Tourism Cromwell board members Glen Christiansen and Emma McDonald and race director Terry Davis to organise the event.
The idea came from Tamati, who had been asked to arrange a "sister race" in New Zealand to complement the Badwater Ultramarathon - a 217km run in the United States, from Death Valley to Mt Whitney.
The idea grew from a speaking engagement at Cromwell last winter where she met Mr Christiansen, who collected her from the airport at Queenstown.
"I mentioned to Glen about the race and he said he knew the perfect place - Northburn Station. By the time we'd driven to Cromwell, we had it half mapped-out."
Mr Pinckney, himself a multisport athlete, was happy to be involved. He sees the event helping to publicise his 12,947ha merino and beef farm, which also features a vineyard, restaurant and function venue.
"One of the advantages with having it here was there was no red tape - no traffic management plan needed. And, although the number of competitors is low this year, we're happy at that.
"It's a starting point and we're sure it will grow."
Finishing times are an "unknown quantity", but the official cut-off times are 48 hours for the 160km race, 30 hours for the 100km event and 12 hours for the 50km.
Tamati says the stunning scenery is a drawcard in itself.
Some of the top ultra-distance runners from this country and overseas have entered the event - Samantha Gash, from Melbourne, in the 100km, and Martin Lukes, of Christchurch and Matt Bixley, of Dunedin, in the 160km race. Gash says the course is going to be tough.
"It's very steep and one of the toughest 100-mile courses I've seen.
"The most important thing you need is mental strength.
"The course will be hard on the body but keeping going for that long - for up to 48 hours - comes down to mental strength.
"While you're running for that length of time you go through every possible emotion.
"Going over difficult terrain you have to pay attention to every footstep and that tires you out. Of course, that's magnified when you're running through the night."
She would be "grazing all the time", snacking on fruit, dried fruit, power bars and cold cooked sweet potato, eating about every 45 minutes.
Mr Pinckney said although the weather forecast was for rain, he was sceptical. The area was among the driest in the country but there was a "plan B" for a different course if the weather was bad.
