It started 6 years ago with 67 runners from New Zealand and a single competitor from the USA. On March 15 the 6th Vibram Tarawera Ultramarathon will have a field of over 850 runners from 26 countries, including some of the very best ultra distance runners in the world.
The long distance running event from Rotorua to Kawerau is in one of New Zealand's most scenic regions, the appropriately named Bay of Plenty.
And in 2014, it will be one of the races in the new Ultra-Trail World Tour - 10 events in Europe, Africa, Asia, USA, Australia and New Zealand.
The Tour includes some of the biggest and most prestigious running events in the world.
The inaugural tour kicks off with the Vibram Hong Kong 100K in mid-January.
Race two is the North Face Transgrancaria in the Canary Islands on March 1 which marks the start of the European race season.
The tour is giving more runners in the international community a bucket list of top races all round the globe to experience and had an instant impact on the Tarawera Ultramarathon, race three on the calendar.
Among the 175 overseas entries this year, there's a big boost in runners from Australia, coupled with a lot more runners from Hong Kong, mainland China, France and the United States.
"Most of the athletes will be tackling the 100 kilometre option – the toughest challenge available to the Tarawera Ultramarathon runners and the relay teams," says race director, Paul Charteris.
"Add those running the 60 and 85 kilometre options and the relay runners and it's a huge field - far more runners than any other ultramarathon running event New Zealand's ever seen."
Most of those runners are first-timers to ultramarathon running.
Support crews, friends, family, media, volunteers and spectators will add another 1500 to 2000 people. They will fill up accommodation during race week and take the opportunity to experience everything a well-established tourist destination like Rotorua has to offer.
Ultra distance runners are some of the most stubbornly, persistent and patient of all athletes.
Standing at the start-line, they know it may be twelve hours or more before they reach the finish line.
"Successfully running an ultra is as much a combination of patience, strategy and perseverance as athletic ability," continues Charteris. "You tend to get pretty good at visualising the finish-line and spending all day running in the forest gives your mind plenty of time to think."
Building the Tarawera Ultramarathon was a similar process of hard work, patience and perseverance for Charteris. The number of athletes, spectators and media gradually increased each year.
Then there was an explosive growth curve for this year after the Tarawera received UTWT status. Numbers are double the entries in 2013.
"Fortunately, we've a number of longstanding local partners like Destination Rotorua, Te Puia, the Rotorua Holiday Inn and Abracadabra Café and Bar," says Charteris. "These guys really know how to look after large numbers of people."
It was a very different story back for the Tarawera Ultramarathon back in 2009.
"I don't think we had enough race entries to even cover the cost of getting a t-shirt printed for that first race," says Charteris, with a chuckle. "Now, we're at a point where the event is starting to inject some serious money into the Rotorua business community."
He and his team are also planning where to accommodate the international running media that will be following the event.
"The spotlight will really be on the Bay of Plenty and New Zealand in March with our first 2014 video promo already getting lots of views on YouTube," Charteris says. "Ultra-Trail World Tour events will also all be broadcast on Eurosport TV, with over 120 million viewers in Europe and Asia. It really is massive exposure for the event, the region and our country," he adds, before heading out for a well-earned run in Rotorua's Whakarewarewa Forest, where the race will start in two months, "to have a think about all of this."