Auckland's underground lava tunnels unveiled in 3D exhibition

Beneath our feet lurks an ancient world rarely explored by those above the surface.

It has existed for up to 40,000 years, more recently under the streets and houses of Auckland, with very few humans ever setting foot within.

You may even have an entrance buried in your backyard.

But now these volcanic tunnels have been made accessible through a series of 3D images that make up the Into The Underworld exhibition, beginning on Saturday and running through to December 24 at Silo 6, on the Wynyard Quarter.

They're a compilation of work done by speleologist Peter Crossley over 50 years and, over the past couple of years, digital artist and architectural graduate Chirag Jindal.

Mr Crossley has spent much of his career locating and documenting these subterranean caves, formed by the lava flows from the city's 50 volcanoes.

But Mr Jindal's intervention, using a $100,000 LiDAR (Light Detection Ranging) scanner, has brought that passion to life for those not lucky enough to have seen what Mr Crossley has seen.

garden shed
Garden shed leads to lava tunnel. Photo credit: Chirag Jindal

"In the most ideal scenario, we would take all of Auckland down to the caves, but that's not possible," says Mr Jindal.

"We're not the Waitomo Caves, we can't fit a thousand people into these caves, because they would get absolutely ruined.

"So the question is how do you show the public what they are without taking them down there?"

The images are far more effective than photographs in illustrating the tunnels and their relationship to the world above.

"Photographs in a cave are actually quite difficult, because they have no light and you need light for great photographs," says Mr Jindal.

"Photographs are flat and don't really give you a sense of scale, which is quite important when it comes to these sites.

"Where the 3D scanner differs is you're not only capturing the environment in a great amount of detail and accuracy, but you're also able to generate a model of the surface, as well as the cave below."

While many of these tunnels have caved in over thousands of years, creating the openings that now form entrances, Mr Jindal insists they are structurally strong and capable of supporting the urban infrastructure that now sits above.

tunnel house
Tunnel incorporated into house design. Photo credit: Chirag Jindal

"Because they've been around for 40,000 years, their typography is an arch, which is the strongest geometry and least likely to collapse.

"The biggest threat is the demolition of big houses above them. It's mostly the excavation that occurs above the surface and weakens the ground above the cave, which tends to collapse as a result.

"We were scanning in a cave at Three Kings and we were literally under a road - we were about a metre-and-a-half underneath and you could hear cars driving above you. At first, it was a bit of a harrowing experience, but you get used to it."

Because many of the cave entrances sit on private property, access is limited, but Mr Jindal suggests anyone hoping to explore them should head to Rangitoto Island, where the tunnels are open to the public.