'I can think of no other edifice constructed by man as altruistic as a lighthouse," George Bernard Shaw once said. "They were built only to serve."
Even after the leap in navigational technology represented by GPS, they maintain that historical function: shining a light for miles around, warning sailors and ships of dangers lurking beneath the surface.
The way they are powered is changing, though, and with it the work of the people who tend them.
The tradition of constantly manned lighthouses ended on March 24, 1997, but the lightkeepers' cottages are still inhabited for weeks at a time by maintenance staff who service the lights' diesel-powered motors. Today, Irish Lights workers travel to sites including Fastnet Rock off Co Cork, Tuskar Rock off Co Wexford, Inishtrahull Island off Co Donegal, Slyne Head off Clifden in Co Galway and Kish Tower in Dublin Bay.
By 2025, however, all lighthouses, beacons and buoys dotted around the coast and in Irish waters will be powered by renewables. The amount of work for technicians who stay at remote lighthouses will fall.
Irish Lights, led by chief executive Yvonne Shields O'Connor, is withdrawing from lighthouses' accommodation quarters. Anything that could cause harm will be removed and the fuel systems will be drained.
After 41 years of service, Brian Kelly (65) retired on May 29. When he began working as a lighthouse technical mechanical worker in 1979, there were 600 lighthouse keepers in the country. The move to automation spelled the end of this unique career.
Kelly describes his profession as one of constant evolution. For the first 25 years of his career, he left his family home in Cabinteely, south Dublin, to travel to the other end of the country to maintain lights. Sometimes that meant not telling his children exactly when he would be home; bad weather had a habit of causing disappointment.
He could be hundreds of miles away on Ireland's most remote island - Tory, 14km off the coast of Donegal - when high winds and swelling seas made the journey back to the mainland impossible.
"It was a job I loved - I would've done it for nothing. If you like peace and quiet, you'd be in the right job," says Kelly, who is originally from Ballinasloe, Co Galway.
"What I miss more than anything else is being out on the coast. I miss the freedom and the peace. The job meant you got to see lots of tiny little beaches people can't get to. Ireland is beautiful - we don't appreciate how beautiful it is. We were privileged to see if from a different angle," he says.
"There's nothing like sleeping in a lighthouse on a bad night with driving rain and big waves breaking - it's very comforting.
"But if you're a light sleeper, you won't sleep well," he says.
A bird's-eye view
Of all the lighthouses, Kelly's favourite is Kish Tower, a landmark well-known to sailors and ferry passengers passing through Dublin Bay.
For Malcolm Gillies (44), from Drumconrath, Co Meath, who trained as an electrician before joining Irish Lights, maintaining lighthouses has given him a bird's-eye view of some of the island's most beautiful places.
In his 17 years' service, the job meant 150 days a year away from home. It often meant being sent on a rock off the coast with all his provisions for three weeks at a time.
"You do feel privileged when you're in these places - only a small minority of people will ever see them in their lifetime. I've spent a lot of time on Fastnet and it is a unique experience," says Gillies.
He describes having dinner there as being a bit like eating in the most exclusive coastal restaurant, with a 360-degree view from the top and the most beautiful sunsets imaginable.
There were negatives, though. "There are days when you're on a rock for two weeks and you have down days," he says. "The helicopter may not be able to land because of wind or fog. You have to dig into the reserve of food and keep the humour up. As people retire, they aren't being replaced. There's enough of us to cover things at the moment, but technology has a grip on things now," he says.
Gay Mulvey's family has held various roles with Irish Lights since 1934, and the Dún Laoghaire man's retirement this year marks the end of an era.
Mulvey says the change has been so gradual it barely registered. While he admits there is a certain romance to lighthouses, he won't miss the smell of diesel or the noise or the dirt of working with engines.
Despite the long periods away from home and family, he says he loved the job. He recalls one evening on Skellig Michael off Co Kerry when the puffins came out and walked around him as he sat stock-still watching them.
Another fond memory is of swimming in a "natural swimming pool" in the rocks at Slyne Head off Clifden, Co Galway. "When the tide went out on a sunny day, the water would heat up and we'd be able to swim there," he says. "People would pay thousands for it."
He remembers being stranded for days at Bull Rock off Dursey sound in Co Cork, which looks like something from a pirate movie, with a passage through the rock.
After 44 years of spending time on lighthouses, he says what he will miss most is the camaraderie. "Whether you like someone or you don't, you have to find a way. There's a circle of us who are buddies as well as colleagues. You can't be on a rock for three weeks at a time without some friction. There's a lot of psychology and of biting your lip," he says.
Mulvey explains that each lighthouse has a different 'character', by which he means the flashing sequence of the light. "It could be four flashes every half minute or three flashes every 40 seconds. That character is unique to that light within that zone," he says.
"The ships have to know where they are. It sounds primitive with all the technology we have in this day and age, but internationally, they still want the lighthouses. It's absolute certainty. There's no wondering about [the lighthouses' signal]. Ships can tell exactly."
Robert McCabe, the director of coastal operations with Irish Lights, says that lighthouses are far from a relic of a not-so-distant past. Despite all the developments in GPS navigation, he says, mariners and ships are resolute that they want the lighthouses and buoys maintained.
McCabe says huge advances have been made in navigation since he first went to sea as a cadet in the 1970s. He calls GPS a 'godsend', but points out it is not infallible.
A report entitled 2030: Navigating the Future commissioned by the lighthouse authorities of Ireland and the UK identified an overwhelming reliance on GPS, with its inherent vulnerability to man-made interference and space weather.
"The big fear nowadays is deliberate jamming of [GPS]," McCabe says. "If you were in a busy shipping lane, that could cause havoc. The mariner still wants to be able to say, 'I still have my old skillset' and they want to be connected with the world outside the window. We have spent about two years talking to people.
"The big ships value the lighthouses much more than people might think," he adds. "There's no sense that their value will disappear."
Lighthouses have been symbols of both romance and tragedy for generations. They have often been remote and untouchable, but in recent years many have opened to the public, with some available for self-catering accommodation.
The Irish Landmark Trust, in partnership with Irish Lights, has 14 lighthouses in the Great Lighthouses of Ireland portfolio dotted around the coast. Having reopened for business at the end of last month, the idea is to give people and up-close experience of these structures' role in the island's maritime story.
At Fanad Head lighthouse (inset) in Co Donegal, which has been voted one of the world's most beautiful lighthouses, you can stay at one of three lightkeepers' cottages, which were restored in 2015.
At Wicklow Head, the Irish Landmark Trust transformed the 239-year-old octagonal stone tower into self-catering accommodation, including 109 steps up into the kitchen.
Fastnet Rock, near Cape Clear in Co Cork, is not available to visit but there are boat tours around it.
For more information, go to greatlighthouses.com