Its list of illustrious visitors over the years reads like a Who's Who from history, including Queen Victoria, Robert Burns, Mary, Queen of Scots and Bonnie Prince Charlie to name but a few.
The 12th and current Duke, Bruce Murray, is South African. His father John inherited the title after the 10th Duke, Iain Murray, passed away in 1996 without leaving any heirs. With the title passed on only through male bloodlines, it was bequeathed to another branch of the family tree.
As chief of the Murray clan, the Duke still retains the unique honour of being head of Europe's only legal private army, the Atholl Highlanders.
Behind the scenes an army of workers grafts to make Blair Castle one of Scotland's finest country homes and estates. These are their stories.
MO TRACEY, HEAD GUIDE
If Mo Tracey were ever to appear on BBC quiz show Mastermind, she would have a star turn up her sleeve. As head guide at Blair Castle, the 65-year-old retired primary school teacher possesses an encyclopedic knowledge of its former occupants and many incarnations.
While I stand gawping at the weaponry display in the majestic entrance hall, Tracey rattles off a potted history of how the castle grew from a single tower in 1269, guarding the route between north and south, into an imposing fortress almost 300 years later. "A big, drafty, awful place for living in," she shudders.
During the 18th century it was transformed into a beautiful Georgian home, but by the 1870s the then 7th Duke had some further tinkering in mind. "The Duke looked at his Georgian mansion and thought: 'I'm not in fashion,' so he turned it into what we have today," explains Tracey. "Instead of a pitched roof, he put the turrets back and had his castle on the outside.
"Inside he built this lovely hallway. It was done to impress and even today anyone walking in through that door is knocked out by what they see. It fell right into what was the fashionable style of the day: Scottish baronial."
Tracey has been a guide at Blair Castle since 2006. She grew up in the tenements of Maryhill in Glasgow, but now calls Aberfeldy home. It was always her promise to herself that when she retired she would work in a historical building.
She imparts glorious nuggets as we traverse the grand spaces: the beautiful stucco ceiling that was 10 years in the making; the fireplaces built using marble from nearby Glen Tilt; a collection of snuff boxes that led to the gentlemen of the era sporting giant purple noses.
"Oh, I must show you this," she says, gesturing at what looks like a gravy boat. "Ladies toilet. I spent ages looking for the lip to pour from before I worked out what it was for. They would go behind screens to use it. Some ladies even had hidden pockets inside their big dresses where they would carry one of those around with them."
Among her favourite stories is Queen Victoria's visit in 1844. "She brought 64 servants," says Tracey. "Her staff included a policeman and an upholsterer. The Duke and Duchess moved out because the Queen needed privacy. She then later invited them back to their own house for dinner."
Tracey still gets the same tingle of excitement when a coach load of visitors pulls up each morning. "That gives me a buzz," she says. "When people see the castle for the first time they are mesmerised."
MAJ SUTHERLAND, CLEANER
Duster in hand, Maj Sutherland casts a critical eye around the room. Charged with keeping Blair Castle spick and span, she has impeccably high standards. Her role as head cleaner is arguably not unlike painting the Forth Road Bridge: an endless cycle of polishing, dusting and vacuuming.
"The way the castle is cleaned will never change," she says. "There is only one way to do it. That is old fashioned and traditional cleaning methods dating back hundreds of years. Elbow grease is the main thing. The cleaning products we use are few. Things like Mr Sheen are like swear words around here."
Sutherland, 62, began working at the estate's caravan park in 1980. Five years later, she moved over to the castle. She feels a strong tie to Blair Castle and the estate. "I was born and bred in the village, two doors away from the house I live in now," she says. "Every Sunday after church it was up to the castle for a walk. It was always part of my childhood growing up."
Her philosophy is one of "conservation, preservation and observation". While she notes that "you can't just go to Ikea and buy another one" if something gets broken, to that end Sutherland never wants its staff to feel daunted by the eyewatering value of the artefacts they handle on a daily basis.
"If I said to you: 'See that dish you are washing? That's worth £30,000.' You would think: 'Oh my God …'" she says. "We don't venture down that road. Everything is treated as a precious piece, but it's a good policy not to dwell on the value. It's a case of being as careful and sensible as you can be."
To say her job is varied would be an understatement. "We work with so many different things: weapons, china, furniture, carpets and fabrics," she says. "The fabrics can be challenging to clean. We have wonderful machines called conservation Hoovers that do a fantastic job - but a normal Hoover on a low setting with a nice pair of tights over it works too. That way you aren't going to pull any loose threads."
Sutherland was eligible for retirement two years ago, but has no intention of hanging up her cleaning tabard just yet. "Obviously there will come a day when I will have to cut back and not do so much - it happens to us all," she says. "As long as I can get up in the morning, open those doors and think: 'Yes!' then I will be here."
JANE ANDERSON, ARCHIVIST
When meeting Jane Anderson for the first time, her opening gambit comes by way of an unnecessary apology. "Once I get started on my archive I won't be able to stop," she says with a bashful smile. "I could talk for hours. I'm so proud of it."
You can hardly blame her. As archivist at Blair Castle for the past 30 years, Anderson has what is arguably the most enviable work space in the business, spending her days surrounded by thick leather-bound tomes, yellowing maps and aging photographs, each providing a window into Highland life dating as far back as 1180.
With an office based in the Clock Tower, her main role is to manage the estate records and oversee conservation and restoration work, as well as keep a detailed log of where every item in the castle is displayed or stored. "The first part of the job was the archive, but it's grown to encompass all the contents," she says. "It's always work in progress. It never gets dull."
To mark the centenary commemorations of the First World War, Anderson, 56, has curated a special exhibition. The 8th Duke made the castle available as a Red Cross hospital for convalescing soldiers in 1917, the ballroom serving as the main ward.
One of the nurses, Eileen McCallum, goddaughter of the 8th Duke, filled a scrapbook with press cuttings and mementos. There are also extracts from records the Duchess used to keep track of the men staying at the castle: "Fair hair, nice face," stated one such entry. "Narrow face, very sallow dark eyes" and "crowded teeth, delicate looking" read another.
Anderson would be the first to admit that on occasion the job has moved her to tears. "The 7th Duke's eldest daughter was married to a soldier," she says. "She was Dorothea and he was Harry. One of the letters he wrote had a snowdrop enclosed from where he was during the First World War. I was going through them, cataloguing and reading away: he'd been at the Front and it was muddy, he hoped his wife was OK and was keeping safe in the bombing.
"Then the next one was: 'There is nothing here but mud and these snowdrops.' And there it was. That was the most emotive thing I've experienced out of the whole time I've been here. To think he had been on the First World War battlefield, standing there in all this mud, destruction and killing, but saw this patch of snowdrops and just wanted to send one home to his wife."
GEORGE FARRON, CARETAKER
There is a handsome photograph of George Farron in the official Blair Castle guidebook in which he is wearing the distinctive dress of the Atholl Highlanders. He has a wealth of knowledge on the famed infantry regiment, which has the distinction of being Europe's only legal private army, having been a member himself for 27 years.
Today, however, Farron is attired in the far more practical clothes required of his day job as resident caretaker. Born in the nearby village of Blair Atholl, he took over the job from his brother Hugh, 19 years ago.
Farron is the kind of man you can imagine has a pencil perpetually behind the ear and a screwdriver in his back pocket. Living on the estate year round with his family, it's his role to ensure everything keeps ticking over. "That can be replacing light bulbs one day and tightening up all the screws on the restaurant chairs the next," he says. "I can pretty much turn my hand to anything and everything."
Over the winter, Farron, 54, plays a key part in the meticulous cleaning operation of the castle's treasures, ensuring everything is ready for the first influx of visitors. "It's far from monotonous," he says. "We'll do the guns one day, pot brasses the next. Each year it's a mixture of excitement and panic: is everything going to be ready in time?"
While he retired from the Atholl Highlanders last year, Farron remains involved and proudly gives a tour of the armoury - in a top secret part of the estate - where the ceremonial rifles are kept.
First raised in 1778 by the 4th Duke as a regular military regiment intended to fight in the American War of Independence, the Atholl Highlanders were later disbanded. The current regiment dates from 1839 when Lord Glenlyon took a bodyguard of men to the medieval tournament at Eglinton, Ayrshire.
Five years later, the Atholl Highlanders served as mount guard when Queen Victoria stayed at the castle and for this service were granted her colours and the right to bear arms. The regiment was revived again in 1966 by the 10th Duke and now parades annually.
"It's one of the things that makes Blair Castle so unique," says Farron. "People never fail to be impressed by the story of the Atholl Highlanders."
SANDY REID, FORMER GAMEKEEPER
When it comes to the sprawling 145,000 acres of Atholl Estates, Sandy Reid knows every crease and crevice like the back of his hand. He started out as a pony boy at 15 and worked his way up to head gamekeeper.
Now retired, the sprightly 71-year-old runs wildlife safaris through the rolling glens and lofty hillsides showcasing fauna that includes red deer, white hare, foxes, badgers, pine martens, grouse and pheasants. Reid knows all the best spots to stalk a stag, fish for salmon, catch a glimpse of an otter or osprey and the hallowed locations where golden eagles nest.
"We have red deer - some 7500 of them - then there's fallow deer down at the Dunkeld end and some roe deer here mostly in the woods, but a few up on the hills as well," he says. "We've got two or three pairs of osprey. There is one where I can drive in right directly below the nest. I was lucky enough to get some nice photos of otters at the dam up near Bruar a few weeks back.
"We have two pairs of golden eagles at the moment. They are sitting on the nests right now."
Reid lends me his binoculars to have a closer look at some deer on the hillside. "It's best to get out in the early morning when the deer are down from the hills," he says. "They are the opposite of sheep, you see. They come down and graze at night and go back up in the morning. The sheep, however, they graze in the day then go up at night and lie."
He gestures to the estate stables, a cluster of sturdy ponies visible in a nearby field. "We do the stalking the old traditional way here," he says. "Everything comes in on the ponies. We put the stags and hinds over the back and the grouse in panniers. A lot of other estates started using quad bikes and such like, but it just isn't the same." n
Blair Castle, Blair Atholl, is open daily from 9.30am until 5.30pm. Visit blair-castle.co.uk.