All eyes will be on a pair of returning champions at the 10th Tarawera Ultramarathon tomorrow.
Among the favourites to take out the 102km race are Napier's Ruby Muir, who was the fastest woman in 2013 and 2015, and American Dylan Bowman who won in 2015.
Muir is in hot form, last year she won the National Cross Country Championships (10km) and the Kepler Challenge (60km), and finished second in the National Road Championships (10km).
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In the event's Athlete Guide she said she loved that trail running gave her the opportunity to see "beautiful parts of the country".
"I am excited to race Tarawera due to the competitive field it attracts. I run to challenge myself and having top international athletes coming here is too great an opportunity to miss," Muir said.
In 2016, Bowman won the Ultra Trail Mt Fuji in Japan, which was shortened to 27 miles (43.5km) after a typhoon wiped out more than 70 per cent of the course. Last year he won the 100 Miles of Istria and finished seventh at the Ultra Trail Mont Blanc.
He said he used ultra running as his "alone time and therapy".
"In the two days before any big race, I try to do almost nothing. Just allow myself to be extremely lazy. That way, by the time the race comes, I'm desperate for some activity and excited for the challenge," Bowman said.
Other athletes to watch in the women's race include Cecilia Flori and Amanda Basham.
Flori, who is from Italy but lives in New Zealand, finished third last year and is the fastest returning woman as those who finished first and second are not in attendance this year. She also finished second to Muir at the Kepler Challenge.
Last year Basham won the Ultra Race of Champions in Virginia, USA and in 2016 finished second in the Gorge Waterfalls 100km in Columbia.
Other men who could push for victory in the 102km race include United States runner Cody Reed and New Zealand's Sam McCutcheon.
Reed won the Miwok 100km in California in 2016 and last year he won the Way Too Cool 50km race in Sierra Nevada.
McCutcheon finished third in last year's Tarawera Ultra and is the fastest returning man, as the top two finishers will not be racing. He won the Kepler Challenge in 2016 and 2017.
Overall, including for the 100-mile (162km), 102km, 87km and 62km runs, there are 1350 people entered in the event, which will finish in town - at the Rotorua Government Gardens - for the first time.
It is the first time the 100-mile race has been included and several elite athletes have entered.
The women's favourites include New Zealand's Fiona Hayvice and United States' Sally McRae. Hayvice won the Tarawera Ultra in 2016, the same year she finished second in the Ultra-Trail Australia. Last year she finished fifth in the 100-mile Western States Endurance Run.
McRae finished second in both the Ultra Race of Champions 100km in 2016 and the Sciacche trail 50km in 2017. Earlier this year she won the San Diego 80km.
The favourites in the men's 100-mile race include New Zealand's Grant Guise and Dennis de Monchy.
Last year Guise finished 13th in the Hardrock 100-mile and eighth in the Ultra Trail Australia 100km. De Monchy won the 23km Blue Lake race at last year's Tarawera Trail Marathon and is a former Double Rainbow Mountain 46km champion.
For the event schedule and further information go to taraweraultra.co.nz.