Earlier this month small sinkholes emerged in the Ballarat neighbourhood of Black Hill, an area dappled with historic goldmines and landfills.
Both geotechnical engineers and historians say the shafts hark back to the days of the gold rush in the 1850s.
And in modern times, sinkholes have appeared over the decades on and alongside roads, in parks, and even underneath private properties, because of them.
Geologists say it's nearly impossible to know the precise location of every single shaft or mine as record-keeping has not always been thorough.
But whether a historic shaft is down the street, at the park, or even in your own backyard, how dangerous can they be?
And what options are available for property owners, when it comes to insurance?
Digging up the past
Historically, mid-year is the wettest time for Ballarat, and this year the city has seen drizzle nearly every day since June.
Land-shifts and sinkholes can occur with time and wet weather, and more shifts in the soil could be on the way as Australia moves into spring.
Geologist Haydn Swan has worked in a range of roles in the minerals sector, exploring for gold and diamonds.
Now a senior lecturer in economic geology and applied geochemistry at Federation University, Mr Swan said it was entirely feasible that illegal mining activity once took place in Ballarat, making it now impossible to know the location of every shaft.
"People in Ballarat live their lives and don't think about how much actual mining activities were taking place," he said.
"But there's not many places in … [the] city area that haven't been turned over.
"We sort of have a reasonable idea of where some of the bigger mine operations were. but there's lots and lots of really boutique small operations that were trying their luck.
"And really, we have no clue — they were just everywhere."
'Under someone's back porch
When mines have been exhausted of their elements and are no longer viable, they are "capped".
In the 19th century, this often meant they were backfilled completely with soil, for the shallower operations.
For the larger mining operations, areas were often topped with timber and even rubbish.
But 150 years later, that topping could be breaking down.
"It's often in very inconvenient spots that we don't know — it might be on a boundary fence or under someone's back porch or in the middle of a road," Mr Swan said.
The geologist said it was hard be sure if mining activity took place, though sometimes, there were shallow depressions that could be indicators.
"Anywhere along that … spine of Ballarat, from Mount Helen, Mount Clear, Golden Point through to Black Hill — there's a very good chance that there was a lot of activity through there," he said.
What happens now?
According to the City of Ballarat council, when sinkholes do develop, the organisation's operations team "responds as soon as possible once they become aware of the issue".
The council's director of infrastructure and environment Bridget Wetherall the team would attend the site and secure the area with fencing for public safety prior to investigating the possible cause of the sink hole.
"This assessment includes determining if there are any known mineshafts in the area … once the area is assessed repair options include capping or filling the sink hole," she said.
Modern-day methods of capping include topping the sink hole with concrete.
"Public safety is always our highest priority when assessing sites where sink holes have developed," she said.
"Ballarat's mining history makes it extremely difficult to monitor when and where a sink hole may occur, but we will always act as soon as possible when we become aware of them."
A history underground
Natasha Joyce is a Latrobe University researcher and historian with an interest in gold-rush communities in central Victoria.
Ms Joyce has been researching the danger historic mine shafts have posed throughout history.
She said there had been dozens of accounts of people and animals falling victim to sinkholes over the past 150 years.
"If you go back through the newspapers, right back to the very beginning, there's always stories of children falling down mine shafts," Ms Joyce said.
Ms Joyce said mining operations across Ballarat and central Victoria were so widespread, evidence could still be found today if you knew what to look for.
"And if you think about it, the land around this area was just completely turned upside down … so there are holes everywhere," Ms Joyce said.
"And [they] could be anything from just a few feet deep to literally hundreds of meters deep."
What recourse is available for home owners?
A spokesperson from the Insurance Council of Australia (ICA) encouraged home owners to be aware of whether their property was located near or on top of a historic gold mine.
"Home insurance typically covers damage to a property caused by unexpected events, like fire," the spokesperson said.
"However, policies may vary when it comes to coverage for sinkhole damage.
"The ICA encourages home owners to talk to their insurer if they are concerned about the risks of a sinkhole and make sure they have the appropriate insurance coverage.
"[And] to have a good understanding of the risks of living in certain locations where the likelihood of a sinkhole appearing may be higher than normal."