It is undoubtedly the most famous and oft-captured image portraying fantasy Scotland – trumping even the buttocks of Mel Gibson in Braveheart. It has adorned a million biscuit tins, countless postcards and tea towels and it attracts thousands of visitors each year to take selfies with the crenellated battlements in the background while swatting away midgies.

Eilean Donan, at Dornie by the Kyle of Lochalsh, is unmistakable, with the narrow footbridge leading to the castle on the water where three sea lochs meet, with the Cuillins of Skye in the far distance. It has featured in films like Bonnie Prince Charlie, with the unlikely David Niven in the role in 1948, The Master of Ballantrae with Erroll Flynn (nary a maiden was left unviolated), Highlander and even the Bond movie The World is not enough. It’s a staple of dozens of Bollywood movies too, so if you’re visiting and see a group of dancers in brightly-coloured dhoti practising their steps you’ve come to the right place.

The castle was a stronghold of the Clans Mackenzie and McRae from the 13th Century before it was destroyed, in 1719, by the Royal Navy in the Jacobite rebellion. Three ships anchored up and bombarded the castle and the clansmen and their Spanish allies for three days, reducing the place to rubble and taking dozens of prisoners. It lay as an empty ruin for more than 200 years until John MacRae-Gilstrap bought the pile in 1911 and set about restoring it. So what you see today is a modern-day rendition although, fortunately, sans breeze blocks and polystyrene. It is now owned by a charitable MacRae family trust and the 500,000 visitors a year undoubtedly provide the upkeep.

Scotland surely must have more castles per acre than any other country, and certainly per head of population, with around 3000 and counting – more than the population of Aberfeldy or Drumnadrochit – although some are no more than relics of the past, hardly a stone upon a stone. There’s not agreed definition of a castle – every Englishman’s home is one after all – but it’s generally accepted that it has to be a fortified structure built in the Middle Ages (although that again is debatable) by a ruler or noble. One who was generally carnapcious, didn’t get on with his neighbours and had hundreds of serfs of clans people to provide the wherewithal, a bit like Historic Environment Scotland today.

The latest castle to come up for private sale is Bardowie, eight miles from Glasgow, an A-listed, eight-bedroomed property with a walled garden, tennis court, jetty and frontage to the eponymous loch, which is a mere puddle in water terms. It was built in 1566 and was a stronghold of the Galbraiths and passed on to the Hamilton’s of Bardowie.

Its more recent history is that it was owned by Jack Black – not the Rock School star or it would be no more than sandstone dust now – but the other one, the one who charges thousands to make motivational speeches. He used to be a social worker in Glasgow’s East End so he must wake up every day, even before he makes up a pithy epithet, to thank his lord he escaped the snotty weans and junkies.

To quote the guru: “The greatest gift in life is the ability to think great thoughts and have the strength to take action so that those thoughts become reality in this wonderful and abundant world.”

Er, moving on it seems that Jack sold the castle at the end of 2003 and the present owner is Glasgow vegetable dealer Alex Faithfull (no relation to Marianne) through his company Bardowie Holdings. He certainly lives there, unless he flitted very recently. The castle is now on the market for around £3 million although the agents aren’t confirming the price. (Price on Application only).

The Hollywood star Chris Pine stayed there for a couple of months at the end of 2017 to get into the method for his role in Outlaw King, as Robert Bruce.

Most of the surviving castles are either in public ownership or in charitable trusts. Edinburgh, Stirling and Culzean most famously, although exceptions are Inveraray Castle, the seat of the Dukes of Argyll and now a popular tourist attraction, Stobo Castle a health spa, and the quirky Kelburn, owned by Patrick Boyle, the 10th Earl of Glasgow – continuously occupied by the same family since the 17th century, longer than any other caste – who invited some famous Brazilian artist to graffiti the entire facade which, despite the sneers of the traditionalists, has become a tourist attraction

Castles first arrived in Scotland in the 12th century as royal authority was centralised and rewards were doled out. It was King David 1 who introduced them and encouraged Norman and French nobles to settle here, in an attempt to establish royal power throughout the country.

Robert the Bruce must also take credit, if that’s the proper term, for what became known as “slighting”, that is capturing castles and destroying their fortifications, which he did systematically, after wresting them from English control and presumably slaughtering the survivors. He even destroyed his own ones, at Ayr and Dumfries, Roxburgh and Edinburgh rather than allow them to be retaken by the English.

When gunpowder was invented and guns and cannons evolved in the 15th century the design of castles changed, to the look we expect today, bombardment resistant walls, letter box gun ports and platforms to mount artillery. Ravenscraig, in Kirkcaldy, begun in 1460 and now partially ruined, is reckoned to be the first in Britain to be built as an artillery fort.

If a castle isn’t quite your choice of residence and you are shopping at the top end of the market then what about Boraston House, in Ravelston Dykes Road, Edinburgh, which is a seven-bedroom Edwardian mansion house on the edge of Ravelston Golf Course. Offers over £3.5m. Or a six-bedroomed terraced house in the New Town, four floors plus a roof terrace, at offers over £2.5m.

To the west there are a couple of places in Bothwell, one at Mill Road with five bedrooms and a price tag of £1.29m and a huge and rather ugly looking mansion in Clydebrae Drive with a garden going down to the Clyde at £1.25m.

Or if Perthshire’s your choice there’s a 13-bedroom, 10-bathroom Georgian mansion set in 12.6 acres of manicured grounds plus a two-bedroom cottage for the nanny, in Aberargie for just £1.5m. (The 88 acres of woodland are extra.)

And just 10 minutes from Inverness Airport, at Croy, you can pick up a Highland estate, Holme Rose, with gorgeous A-listed Georgian mansion, eight bedrooms, not forgetting the mile of salmon and trout fishing rights on the river Nairn, complete with cottages and 385 acres, eight miles from Nairn.