Dun Lagaidh occupies a wonderful location above the narrows of Loch Broom along a rocky knoll, which was once an important local strategic fortification for 2,000 years. There are three seperate strongholds on the ridge, each using or incorperating the works or materials of previous ones. The first fortifiaction is dated up to 2,600 years old and was a timber-laced stone walled hillfort, with walls between 8 and 14 feet thick, with a narrow entrance just wide enough for for a person to pass through in single-file. There is evidence that the hillfort and probably its defenders met a grizzly end in flames.

A later circular stone walled broch-like dun was built some 2,000 year ago on the east end of the hillfort, protected by walls up to 12 feet thick, with two sets of door-jambs and a guard cell. This tall tower would have commanded the entrance to Loch Broom and be seen from miles around in all directions.

The final fortifacation built on the site of the previous two was as a simple late 12th century motte and bailey castle. A hoard of silver pennies dating back to the 1230's have been discovered. The coins were found close together hidden under rubble in what was originally a purse, close to the outer face of the north wall. The hoard consists of 22 English sterling coins and two Scottish coins bearing King Willian the Lion. The English coins were all minted in either Canterbury or London.

The tower was rebuilt using mortared stone with an entrance via an intra-mural staircase of 16 steps not unlike that of a later tower-house. Additionally, two stone walls were built to join up with the original hillfort walls to provide the castle bailey. There is no recorded history associated with the Medieval Castle, apart from possible connections with the Norse MacAulay's, part of the powerful MacKenzie Clan.

The rough dirt track to the site is quite steep in places and so care should be taken if you choose to drive to where you can pack just beneath the ridge. Ideally a 4x4 vehicle or walk the road from the last house in Blarnalearoch.