The intricate limestone formations inside the Buchan Caves, in Victoria's East Gippsland, have attracted tourists for generations.
But what their stalagmites and stalactites can tell us about the age of the caves and Australia's mountains is attracting researchers.
A team of researchers from the University of Melbourne's School of Earth Sciences have found evidence that challenges the belief that Australia's mountains aren't growing.
The researchers have used a technique pioneered by the university's Professor Jon Woodhead to test the age of the samples taken from the cave floors.
Using the technique, called uranium-lead dating, the researchers found the mountains in south-east Victoria are growing 76 metres every million years.
"So that may not sound like a whole lot to you and me. But on a geological timescale, that's actually quite a lot," PHD student and researcher John Engel said.
Usually, tension between tectonic plates causes mountains to grow.
For example, Mr Engel said, mountains like those in the Himalayas are growing about 250 metres every million years.
But Australia's mountains are different because they are not on the edge of a tectonic plate.
"New Zealand is right on the boundary between the Pacific and Australian plate," Mr Engel said.
"But all of that activity happening there seems to be propagating inwards in towards the Australian interior.
"It's required us to expand our thinking about what plate tectonics means."
Caves younger than thought
The researchers' work testing samples from the Buchan Caves has also resulted in a major shift in our understanding of the age of the caves.
Previously, geologists believed the caves were 90 million years old. But the Melbourne University team believes they are much younger.
"This new research shows that the caves started forming around three-and-a-half million years ago," Mr Engel said.
The previous estimates were based on rock samples taken from nearby parts of Victoria's highlands.
"Our research doesn't discredit that; it just shows that there's been additional younger pulses of uplift that have happened," he said.
Abseiling deep underground
To do their research, the team had to go beyond the sections of the caves accessible to tourists and into the "wild caves".
Buchan's tourist caves are paved, lit and easily negotiated but getting to the wild caves means abseiling deep underground.
"You've got to crawl through tight squeezes and it's very muddy and humid and it's not for the faint of heart," Mr Engel said.
"We'd go down into the caves and find these pieces of broken stalagmites and put them into a bag and take them back to the laboratory."
He said he would spend half his time in a "muddy tracksuit" climbing through the caves and the other half in a lab wearing a white coat testing samples.
Using uranium-lead testing on broken pieces of cave stalactites and stalagmites — collectively known as speleothems — marks a shift in how young mountains are dated.
Previously, geologists would use a technique called apatite fission track dating, which Mr Engel said wasn't suited to dating younger mountains.
Exciting new technique
"Anything younger than about 15 million years old is really hard to see by the apatite fission track dating and techniques," he said.
"So this new speleothem cave-based one we hope will be an exciting and useful way for geologists around the world to show young uplift."
Collecting already broken samples from the cave floors also minimised the researchers' impact on the caves.
The team's research will soon appear in the peer-reviewed International Journal of Geology, which Mr Engel said was a "really exciting" opportunity to make their work "available to researchers around the world".
"So now they'll be able to use this technique that was created here in Buchan," he said.
