What is it that draws so many people to the Tongariro Alpine Crossing year after year?
They keep coming despite occasional eruptions and reports of climbing accidents - a reminder of what happens when things go wrong in an unforgiving alpine environment.
For our group of women adventurers there is plenty of appeal ... taking on a fresh challenge, learning more about one of our national treasures, and sharing the experience with like-minded souls.
As this is a new experience, we opt for a guided crossing with Adrift Outdoors, a well established guiding company. We wake to a gloriously fine morning. Our guide checks we have the right gear before the minibus picks us up at Mangatepopo Valley, already 1100 metres up in the national park.
A procession of buses loaded with today's trampers are disembarking when we arrive at the start of the trek, so we delay our start to avoid getting tangled up with the masses.
Our gradual climb to Soda Springs is a good warm up for what lies ahead. We take in the colours and textures of lava flows from recent eruptions.
Nothing prepares you for the steep ascent from Soda Springs (1400 metres) to South Crater (1600 metres). Just focus on breathing ... as the air thins. The crater lies between the two active volcanoes, Ngauruhoe and Tongariro, and we marvel at the magnificent views.
Our guide is very familiar with the volcanic terrain and sets a comfortable pace. The sun is well up now so we are down to t-shirts and shorts. I am very grateful for the loan of a trekking pole.
The next stage is another steep and tricky climb to the Red Crater (1886 metres), the highest point on the crossing. Our guide has figured out I am the least sure-footed so lends a hand at the narrowest point of our ascent.
Arriving at Red Crater we are surrounded by spectacular deep ochre and burnt orange rock formations - the result of high temperature oxidation of iron in the rock from the volcanic eruptions.
All downhill from here? Not really The track descends steeply from Red Crater to the Emerald Lakes as I slip and slide on the moving scree for 20 minutes. There is a technique for this but I can't get the hang of it. Unlike the snow bunnies who are in their element, careering down the slope.
The Emerald Lakes live up to their reputation, glistening in amazing shades of aquamarine and deep turquoise - breathtaking against the barren mountain landscape. We find a sheltered spot to munch on our sandwiches at one of the smaller lakes. Extra layers are needed for the slight wind chill at this high altitude.
After lunch we head downhill towards Ketetahi Hut with spectacular views of Lake Rotoraira with Lake Taupo in the distance. On this clear day we can see Taupo on the far lakeside.
Although there are hundreds of trekkers on the mountain making the most of the glorious day, by now they have spread out so we can experience that delicious feeling being at one with nature.
The downhill trek is more difficult and harder on the knees. After 5 hours on the go I have a couple of stumbles (and bruises to show for it later!). Our guide encourages me to have some glucose sweets for extra energy.
For the last hour we walk through mountain beech forest with the soothing sounds of a rippling stream nearby and take a short detour to a waterfall. This lush scenery is a welcome contrast to the volcanic terrain.
I am left with a lasting impression of the historical and spiritual significance of this dual world heritage site and a lasting appreciation for why Maori view these mountains and the national park as sacred.
This alpine trek is not for the faint hearted ... but is a truly unforgettable experience. An amazing journey with a stunning landscape full of contrasts with colours that have to be seen to be believed.
We all arrive back at the hotel deliciously tired and proud of our accomplishments. So we celebrate with a delicious evening meal at the Chateau Tongariro.
The weather in the Tongariro National Park is notoriously variable and can change very quickly so you need to come prepared - good boots, an insulating layer, proper wind and waterproof protection, sunscreen and a hat. We took 8 hours to complete the crossing at a steady pace with some rest breaks and a lunch stop. We recommend employing a guide - Adrift Outdoors were great - we learned more about the history and importance of the area to Maori, and they made sure we were safe and well prepared.