Tartan created to commemorate those who died building Cruachan power station
Built between 1959 and 1965 on the shores of Loch Awe, it was the first reversible pumped storage hydro system on its scale to be built in the world.
It was built by a 4,000-strong workforce, including 1,300 known as "Tunnel Tigers", the men at the forefront of the work who drilled, blasted and cleared the rocks from the inside of the mountain.
Drax Group, which owns the power station, has now unveiled a tartan created in memory of those who died, which features 15 strands of a special dark blue thread to represent those who died.
Ian Kinnaird, head of hydro at Drax, said: "Building this unique power station was an astonishing feat of engineering, completed in challenging conditions.
"The work was physically demanding and, at times, incredibly dangerous. Sadly, during the course of the construction, 15 men lost their lives.
"When we were commissioning this new tartan, we decided it was a fitting tribute to incorporate 15 dark blue threads in memory of those who tragically died - many of whom were very young."
One of those who died was Edward Gallagher, 23, from Donegal, who was engaged to Barbara McCabe, now 81, who lives in the Inverness area.
The couple got engaged on December 21, 1961 and were planning to get married the following September.
However, just before Easter 1962 loose rock in the ceiling of a tunnel fell down, the force of which was so strong it pulled Edward out of his protective footwear.
Mrs McCabe said: "He was such a lovely, lovely man. Eddie's father sent me a telegram and what it said was: 'Is Eddie alright?' I didn't know what it meant, I was busy getting ready for
Eddie coming down so we could spend Easter together.
"He shouldn't have been at work, but he'd swapped shifts with someone else who wanted to go home early for Easter - that was what Eddie was like. He was a great young man, always doing things like that to help people."
Mr Gallagher's father travelled across from Ireland and they went together to the cottage hospital at Oban, Argyll and Bute, where Edward was being treated.
She said: "When I saw Eddie, there wasn't a mark on his face - but we were told his injuries were so severe there was no hope of survival. He passed away in the early hours of Easter Monday - the 23rd of April 1962."
Commenting on the tartan, she said: "I think it's a lovely way to make sure Eddie and the others who died are always remembered."
Hollowing out the Ben Cruachan mountain in Argyll and Bute was done by hand-drilling two to three-metre-deep holes into the granite rockface.
Gelignite was packed into the drilled holes and detonated, and blasted rocks were then removed by bulldozers, trucks and shovels, before drilling began on a fresh section of exposed granite.
Eventually, some 220,000 cubic metres of rubble was removed.
The 15 men who died are remembered at Cruachan in a mural on the wall of the turbine hall at the heart of the power station and now visitors to the Hollow Mountain visitor centre will see the new tartan waistcoats worn by guides and on scarves for sale in the visitor shop.
The new tartan, made by Kinloch Anderson in Edinburgh, is based on the Clan MacColl Sett in a nod to Sir Edward MacColl, the pioneer of Cruachan power station.