Two pensioners could be faced with a huge repair bill after part of their garden gave way under an old mine shaft near Aberystwyth.
The mine shaft is close to a public right of way
David and Janet Davies, from Taliesin, were unaware the lead mine existed.
The 35ft deep opening, which could date back to Roman times, has been fenced off as a right of way runs pass it.
The couple have been told they are responsible for filling in the hole, but Ceredigion Council is looking at whether a grant might be available.
Mr Davies, 71, a former businessman, and Mrs Davies, 69, a retired teacher, moved to Taliesin in 1987.
Ceredigion is "littered" with lead and silver mines, many of which were used up until the mid-1800s, mining historians have told the couple.
The couple claim they knew nothing about the shaft, located about 50ft from the front door of their bungalow, when they purchased their retirement home.
Part of their garden collapsed last month.
"We've heard rumours that it could cost up to £80,000 to fill in the hole and we simply can't afford that," said Mrs Davies.
"We've been told by the council that the land is ours and we have responsibility for the hole, but we didn't know the mine shaft was there."
Mrs Davies said there was no evidence in the home's deeds that a mine shaft existed.
"I think it's unfair that we're expected to foot the bill for this when we had no idea the mine shaft existed," she added.
The fenced off area round the mine shaft in Taliesin
Local councillor Ellen ap Gwynn said the mine shaft had been used years ago as a village tip, but the waste had rotted away.
"There's a suggestion the mine may go down as far as sea level," she said.
"The legal matter is that it's their (the Davieses') land and they are responsible for it.
"The council is trying to find out if any grants are available to help people in their situation.
"I've raised the issue with the council that people should be made aware that these shafts are dotted throughout north Ceredigion."