Gold mines in north Wales that were last used 100 years ago have been sealed off to protect a new national treasure - a rare species of bat.
Do not disturb...there are bats (not gold) in them there hills
Metal grilles have cut off more than 20 mines in the southern Mawddach Valley, near Dolgellau.
Dozens of endangered lesser horseshoe bats, and a family of otters, now call the caves home.
The Countryside Council for Wales, the Forestry Commission and others are working together on the project.
The bats, which roost on Forestry Commssion land, are said to enjoy life more if there is silence and they are not disturbed.
The new grilles allow the bats out of the caves, but prevent people from entering.
Jonathan Neale, of the Countryside Council for Wales (CCW), who visited one of the mines where 50 bats lived, said: "The wildlife value of these mines is so high that a partnership of countryside organisations has come together to ensure they are protected from disturbance."
Aled Thomas, a forester with the Forestry Commission, and Pauline Barber, a scientific officer with the CCW, have been working closely on bats for the last five years.
Mr Thomas said: "I've been interested in bats for a long time, and when I realised they were using the mines on commission land I was very keen to investigate."
Mrs Barber sees her work as crucial for the future of bats and otter populations in the area.
"They are both protected species, and in different ways their populations say something about the way we treat our environment," she said.
The CCW's Pauline Barber next to one of the new sealed caves
However, Mrs Barber revealed that examination of otter droppings found that they occasionally ate bats.
Gold from mines near Dolgellau has been used in wedding rings for members of the Royal Family, including the Queen and Prince and Princess of Wales.
Last week, worked started on a part of Cardigan Castle, in Ceredigion, to protect the building - and a colony of rare bats - from the elements.
The top of Cardigan Castle's house is being shielded along with the lesser horseshoe's cousin, the greater horseshoe bat.
There are 16 species of bat found in Wales and a law protects all of them and their roosts.