Castle Sween in Knapdale, Argyll, is the oldest standing castle on the Scottish mainland that can be dated with confidence, according to Historic Environment Scotland.
It takes its name from Suibhne (Sven) - ‘the Red’ - a chieftain of Irish descent and ancestor of the MacSweens.
He probably built the castle in the 1100s when Argyll lay outside the Kingdom of Scotland.
The castle is set on a low, rocky ridge overlooking Loch Sween. Its curtain wall, 2m thick and 8m high, surrounded a quadrangular courtyard, though the complex was altered and built upon during the next 500 years, a statement from HES said.
It has been dated to the 1100s given the broad buttresses, which are Norman in style, on the outside walls. There is also an absence of windows and other openings, aside from the entrances.
In the 1200s, control of Argyll and the Isles was in dispute between the King of Norway and the King of Scots.
As part of Scottish efforts to secure control, the MacSweens were replaced as Lords of Knapdale by 1262 by the Stewart Earls of Menteith.
The lordship of Argyll and the Isles was transferred to the King of Scots by King Magnus of Norway four years later.
The MacSweens launched an attempt to get their castle back around 1300 but they didn’t hold onto it for long.
It was recaptured by Robert the Bruce and was passed to the MacDonald Lords of the Isles in the late 14th Century with several MacDonald families serving as keepers.
In 1481, James III of Scotland, fearful of the MacDonalds’ treachery, entrusted the castle to the Campbell earls of Argyll.
With the Campbells supporting the Covenanters, the castle was attacked in 1644 by supporters of the Royalist cause with Sir Alexander MacDonald finally destroying the property three years later in 1647.
Excavations at Castle Sween suggest the site was occupied long before the castle was ever built.
A stone axe and whetstone was found in a cave beneath the castle in the 1920s with a Neolithic six-knobbed stone ball, three medieval brooches and a barbed and tanged arrowhead also discovered.
Further excavations in the 1980s found evidence of at least five separate periods of use within the courtyard. One notable find was a 1400s harp-peg found on the site, associated with the Lords of the Isles, HES said.
Aberdour Castle in Fife was thought to be Scotland’s oldest castle for some time but it is now believed to have been built slightly later than Castle Sween.