A small group of intrepid Kiwis are delving deep into long-abandoned gold mines in the hopes of documenting history and rescuing artefacts they say are "rotting away".
Karl, who preferred not to give his surname, runs a small team of explorers called The Urbex Crew - their name derived from "urban exploration".
Their Facebook page has amassed more than 9000 likes, and they've also partnered with another exploration page called Derelict NZ, which boasts more than 25,000 likes.
Karl and his partner previously had a keen interest in exploring abandoned buildings, but lately have shifted their attention to mine shafts, most of which were abandoned decades ago.
The Department of Conservation, however, is warning that entering abandoned mines is extremely dangerous, and that those who choose to do so must understand they are putting themselves at significant risk.
Karl's most recent expedition was over the past weekend, during which they entered several mines close to Thames.
"Mainly the motivation is to show people New Zealand mining history," Karl said.
The first recorded gold strike in the Coromandel was in June of 1867, and the peak gold rush came between 1869 and 1871.
"There are some other motivations there," Karl said, "like getting artefacts for museums and that - but we're still trying to work through the legality of that."
The Department of Conservation said while it is legal to enter the abandoned sites on public land, it is very risky.
A spokesperson for the Department of Conservation said "at some locations where there is no current mining, people can enter the sites - but they need to go properly prepared and be very cautious," they said.
"There is a level of risk in exploring these locations (as there is with many sites managed by the Department of Conservation) and people need to understand that.
"In some cases, the Department of Conservation excludes the public from accessing an old mining site based on the safety of the site – although people are free to enjoy public conservation land, there are some locations where mining activity has occurred (and where mining continues to occur) where there is clear and present health and safety risk.
"People should be cautious, go properly prepared, keep themselves safe, and let a friend or family member know where they are going and how long they expect to be.
"We strongly advise visitors not to enter these sites alone and they should be aware of the risk they're taking by entering."
Karl said if explorers like him don't go down the mines and document their contents, as well as securing any artefacts within for preservation, Karl says they'll be gone in no time.
"You end up with the thieves going through there and then they'll sell all the items off for a little bit of money - but these items should be going to museums," he said.
Karl said he had personally heard from people who had bought mine artefacts at second hand stores in the area.
A DOC spokesperson confirmed that taking historic material from a conservation area is an offence under the Conservation Act.
"It is also an offence to interfere with or damage in any way historic or natural features of or on any conservation area - removal of items from a heritage site would be considered as damaging the site," the spokesperson said.
Archeological sites dating to pre-1900 - which many of the Coromandel mines do - are also protected under the Heritage NZ Pouhere Taonga Act 2014.
"From a heritage management perspective, the ability to understand an artefact or a site is associated with context," the spokesperson said.
"So if material is removed from a site, it not only impacts on the understanding of that place, but the item removed, without the site context also loses its ability to tell the story of its use, and the development and use of that place."
There are a few mines in the Coromandel area which are open to the public - mines which have been made safer by restoring the support beams and walkways - but Karl and his crew prefer lost and forgotten mines where prospectors searched for their fortunes more than a century ago.
Karl takes a rational view to talk of ghosts, or supernatural forces inside the mines.
"You get a bit of an eerie feeling," he said.
"I don't personally do the ghost hunting stuff, myself, but there are teams that follow us and do."
He shared images captured inside two of the mines, showing incredible rock formations, flooded passageways, mine support structures and an underground workshop.
Sometimes, there are even treasures to be found.
"We do find a lot of crystals in the tailing piles - we know a couple of people who have managed to find small bits of gold, but nothing too impressive," Karl said.
"All these mines here are only speck gold - you'd need to take a ton of rock out and crush it to get an ounce of gold."
The hobby is definitely not without its hazards and Karl warns that these mines are among the most dangerous places to explore if you're not prepared.
"There's some very tight places we get through, we call them rabbit holes," he said.
"You've got to squeeze through them and they can be very dangerous.
"We definitely don't encourage people to go into these areas."
During his first-ever mine exploration, Karl and a group of friends descended a 60-metre ladder into darkness, went through a small tunnel, then down another 10-metre shaft.
After reaching the bottom, they found a chamber with remarkable rock formations and crystals in the walls - but soon realised it was a very dangerous place to be.
"We were just circling around this room for about 10 minutes and my foot went through the floor where we dropped down," Karl said.
"I looked down the hole, and there was a big, huge shaft under there - my torch only went about 50-70 metres at that time, but I couldn't see the bottom."
The Urbex Crew are now trying to raise funds to purchase better equipment for exploring the mines, including ropes and air quality monitoring devices.