Mills were once the powerhouses of the economy in the north of Ireland, but what has become of the many buildings that drove its industrial expansion?
One man is on a mission to find out - amateur historian Sebastian Graham spends his spare time mapping all of the mills in Northern Ireland.
To date, he has found records for more than 3,000 mills.
He is creating an online database, with details of their owners, photos of the mills and stories from former workers.
"My aim is to record as many as possible before they are demolished," Mr Graham told BBC News NI.
'A couple of hundred thousand minutes'
Guided by Valuation Office records, history journals, newspaper archives, historic maps and the personal memories of former mill staff, he has been building the database for the last three years.
It contains details of former linen mills, corn mills, windmills, saw mills, and flax spinning sites, many of which have been demolished or fallen into dereliction.
"Literally, every day I come home from work, I spend an hour or two going through the old records and putting it out online," said Mr Graham.
From his computer history, he estimated he had spent "a couple of hundred thousand minutes" working on his database.
"I don't know how long that is in hours, or weeks, but it's very labour intensive," he said.
For the record - 200,000 minutes equates to 3,333 hours, 139 days or, if you prefer, four-and-a-half months.
He admitted that mapping old mills from a computer in his bedroom may seem like an unusual hobby for a 25-year-old.
"It's bizarre, I'm sure, for a lot of younger people - they probably wouldn't have much of an interest at this stage, but when they get older in life, they'll be interested, I'm sure," he said.
The private research project is a bit of a busman's holiday for the National Trust tour guide.
Mr Graham has been working at Wellbrook Mill outside Cookstown, County Tyrone, for the last eight years, hosting tours of what is thought to be the last working water-powered linen beetling mill in the UK.
Beetling, in case you were wondering, is a mechanised process in which fabric is pounded with wooden blocks to produce a glossy texture - a finish highly sought-after in the textile industry.
As former mill workers weaved him tales of a bygone era, Mr Graham was inspired to preserve some of the rich tapestry of Northern Ireland's industrial and social heritage.
'Smiles and tears'
"It's not just about the historical information - it's about the workers and their stories," he said.
"It's absolutely fascinating, because that's information that very rarely appears in books - you can't really capture it except when you are talking to them.
"I was talking to a gentleman outside Whitecross, County Armagh, last week and you could see it, just in his eyes, when he was talking about pulling the flax and being in the flax dam.
"If you get the right questions out, it brings back memories to them and you can see the smiles and the tears when they're laughing."
Linen manufacturing was difficult work in damp, dirty conditions and as the former Whitecross mill worker told him, it had some unfortunate side effects.
"They couldn't go out to the dances because of the smell they brought with them, so it was very amusing to hear what they came up with," said Mr Graham.
Despite the stink, the linen industry transformed the north of Ireland economically and culturally in the late 19th Century.
Belfast grew rapidly from a small town into an industrial city and by 1891 it had overtaken Dublin in terms of population size.
Today, the Northern Ireland Assembly uses a motif of the flax plant as its logo, in recognition of its historical importance to the economy.
Game of Thrones
However, the introduction of cheaper, man-made fibres in the early to mid-20th Century unravelled the whole industry, and many mills were abandoned.
Though some have fallen into dereliction, others have moved with the times and ground out new identities for themselves, fit for the 21st Century.
A few are being used for purposes far removed from that which the buildings were originally designed.
Perhaps the least run-of the-mill transformation is that of a former linen manufacturing site in Banbridge, County Down.
Now known as the Linen Mill Film and Television Studios, it has played host to productions such as the hit US TV drama, Game of Thrones.
Staying with the artistic theme - Mossley Mill in Newtownabbey, County Antrim, took on a completely new role after it was saved from demolition in 1996.
The former flax spinning site, which dates back to 1834, was extensively renovated by the local council and is now home to the Theatre at The Mill.
In Belfast, the award-winning regeneration of Conway Mill created a community hub in the west of the city.
The old flax mill, which dates back to 1842, now hosts an education centre, artists' studios and a number of businesses.
Mr Graham is a fan of such projects, preferring renovation to demolition.
"I'd rather see it being used for some other purpose, but incorporating the history behind it," he said.
"I know Conway Mill does incorporate that with a lot of its work."
However, a mill owner in Dungannon, County Tyrone, is determined to keep his family tradition alive.
Ennish Mill has been in Harold Bennett's family since his grandfather bought the building in 1917.
It closed as an industrial mill in 1950, but 50 years later Mr Bennett began to renovate it as an industrial heritage site.
He is being assisted by members of the Killeeshil and Clonaneese Historical Society.
According to Jonathan Gray from the historical society, Ennish is now is believed to be one of only three working scutch mills remaining in Northern lreland.
Scutching is the process of removing flax fibres from the plant's woody stem, in order to make it easier to spin into cloth.
Mr Gray told BBC News NI that Mr Bennett even managed to track down the original diesel engine installed by his grandfather during World War One, repairing it himself.
The regeneration is an ongoing project, aimed at enhancing public knowledge of the "golden age of the linen industry".
It hosts regular open days, with the next planned for Saturday 13 May.
Mr Graham said many other mill sites in Northern Ireland had potential for restoration, but added that it was very difficult to secure financial support.
"People are interested in hydro-electric power - they're very interested in fact - but it's just getting the right funding that is the real killer," he said.
"There are bigger mills around Belfast, Gilford, Lisburn, Sion Mills, they are all mills that have been wrecked and ruined.
"It's very difficult to keep them standing."
It is also a tough grind for one man to track down records of all of Northern Ireland's mills, past and present.
Mr Graham is looking for help from the public to compile his database, including contributions of old photographs and stories.
He can be contacted at his website - Mills of Northern Ireland.