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This impressive fortress is in a very remote location on Loch Sween's eastern shore. It is one of the oldest known stone castles in Scotland yet survives in near-complete condition. Castle Sween is a site of Historic Scotland and is open to the public.
Visiting Castle Sween
Parking
Visitor parking is NOT available near the castle site - There is a sign-posted lay-by for parking located about a 20-30 minute walk away.
Price
Free
Opening
Castle Sween normally is open year-round
Location & Access
The castle is located in Knapdale on a minor road off the B8025, 15 miles (24.14 kilometres) southwest of Lochgilphead on the eastern shore of Loch Sween.
Know Before You Go
- Rough terrain - Strong footwear is recommended
- Restrooms are available on site
- Some areas are not accessible by those with limited mobility
History of Castle Sween
The early history and establishment of Castle Sween links to the legacy of the Norse invaders and highlights the dominating sea power of western Argyll. In Scotland, it is believed to be one of the earliest stone castles.
Time Line
-c.1100
An Irish prince of the O'Neill dynasty settled in western Argyll and founded several families, including Gilchrist, MacLachlan, and Lamont, among others.
-c.1140s (Castle Built)
A descendant of the prince, Suibhne "the Red," Lord of Knapdale, is credited with building Castle Sween around this time. Though not a part of Scotland, Argyll was under Norse control; the western coast's sea lochs were ideal for harbouring warships, and Castle Sween likely was used to beach small galleys.
The stone castle was constructed into a rectangular curtain wall and was probably enhanced with earth and timber defences to encircle a landing point to protect Suibhne's ships.
Suibhne the Red was a powerful chieftain, and his descendants--known as the MacSweens--held lands stretching from Loch Awe to Loch Fyne until the late 13th-century. (Note: In Gaelic, 'bh' is used to create a 'v' sound, and Suibhne was later anglicised to Sween.)
-1260s (MacSweens Replaced)
Control of Argyll has been in dispute between Norway and Scotland, and the Stewarts, Earls of Menteith, replaced the MacSweens as Lords of Knapdale in an effort by the Scots to secure the domain. Following the 1266 Treaty of Perth, Argyll was officially made a part of Scotland.
-c.1300 (MacDonalds Obtain Castle)
During the Wars of Independence, John MacSween attempted to retake the castle but was unsuccessful. Following his accession to the Scottish throne, Robert the Bruce granted the castle to his supporter, Angus Og MacDonald of Islay, and later to his son, John MacDonald. Records indicate that a new, three-storey tower was also built around this time.
-1310-1314
King Edward II of England formally granted the ancestral lands of Knapdale to John MacSween and his brothers on the condition they depose John Menteith. Yet England's fortune was waning, and following their defeat at the Battle of Bannockburn, the MacSween claim fell through.
Historians say it's possible the Gaelic poem Dál chabhlaigh ar Chaistéal Suibhne ("An arranging of a fleet against Castle Sweeny") is about MacSween's claim to the homeland his family lost and refers to his attempt to retake the castle at this time.
-1323
John Menteith died and passed the Lordship of Arran and Knapdale to his son.
-1353
Charters from this year document that the lands in Knapdale were granted to Sir John of Menteith and Castle Sween was granted by Menteith to Sir Archibald Campell of Lochawe.
-1376 (Lands Split)
King Robert II of Scotland granted half of Knapdale to his son-in-law, John MacDonald I, Lord of the Isles. This included Castle Sween. However, the MacDonalds never used the castle as their primary residence and entrusted the site to their kinsmen, the MacNeills, instead.
-1473 (Lands Returned)
The MacMillians become keepers of Castle Sween when Alexander MacMillian succeeds his father-in-law, Hector MacNeill, and the MacDonalds have the castle and lands returned to them.
-1475
John MacDonald was determined to be providing food and shelter for rebels and has his mainland territories forfeited to the crown.
-c.1481-1490 (Campbells Obtain Castle)
King James III of Scotland granted the castle to Colin Campbell, Ist Earl of Argyll; The Campbells of Auchenbreck were appointed as its keepers.
-1615
The castle was the meeting place for the 7th Earl of Argyll's crusade against the MacDonalds.
-c.1644-1647 (Castle Destroyed)
During the War of the Three Kingdoms, the Campbells used the castle as a distribution center for imported supplies destined for one of their many other garrisoned castles. Later, Alaisdair MacColla, a descendant of the MacDonalds, set a vindictive attack on Castle Sween, causing significant damage that was never repaired, and the castle was soon abandoned.
-1933-Present
Care of the castle was given to the Historic Building and Monuments Directorate in 1933; today, Castle Sween is a Historic Environment Scotland site and open to the public.
Castle Sween Occupants
The castle was first occupied by Clan MacSween until the mid-13th century when it was passed to the MacDonalds. Later, the Campbells held the castle, with their appointed castellans first as the MacNeills and then the MacMillans.
Images of Castle Sween






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Castle Sween Q&A
What Type of Castle Was Castle Sween?
Castle Sween was an enclosure castle, built as a rectangular curtain wall and augmented on the North and West sides by two towers.
When Was Castle Sween First Built?
Truly authoritative records of when Castle Sween was first built do not exist. However, the popular belief is that Suibhne the Red chose to build a castle on the site "at some time" in the late 1100s, with others suggesting circa 1100-1150. The castle has certainly been dated to the 12th-century based on the outside walls' broad buttresses and the lack of windows.
The curtain-walled enclosure is widely regarded as mainland Scotland's earliest surviving medieval masonry castle. Radiocarbon data and analysis of stone samples have suggested a 95.4% probability that the curtain wall was finished in 1070-1315 (cal AD).
How Big Was Castle Sween?
Castle Sween initially comprised a curtain wall about 2m (6ft) thick and 8m (30ft) high surrounding an open courtyard. Wide, Norman-style buttresses in the center and the angles strengthened each wall. At some point in the 13th century, a range was added and later heightened into a three-storey tower. Another round tower, the MacMillian tower, was also raised to enhance defences.
What Was the Main Use of Castle Sween?
The castle was constructed by the ruler of Knapdale as a safe harbour for his warships. The site allowed for the small ships of the day to be pulled from the sea, as there was no natural anchoring spot nearby. It appears as though the structure was intended for offensive use. Indeed, we still see evidence of this centuries later when the Campbell family held the castle.
Once the castle was damaged in 1647, it seems as though it was no longer of military value; however, archaeological excavation in 1989-90 found kilns and a forge, suggesting the castle remained in use for industrial purposes. Yet it's unclear precisely when the castle ceased to be of service altogether.
Does Any of Castle Sween Still Exist?
Significant stone remains of Castle Sween still exist for visitors to see today. The sizable gateway entrance leads into its large courtyard, still enclosed by all four walls. The MacMillian Tower is now but a hollow shell, though its former glory is easily imagined with the details that have survived. Meanwhile, the basement has a seemingly complete bread oven and a waterspout set in the kitchen wall.
Most of the parts on the seaward side are mostly gone due in part to coastal erosion, yet the unusually large latrine tower is in a very good state of repair and accessible via a wooden staircase.
Location of Castle Sween
The remains of Castle Sween are set on a low and rugged ridge along the scenic shores of Loch Sween. The southwestern view overlooks the Sound of Jura and the nearby islands toward Ireland, the castle's creator's homeland.