Cairns Castle is though to have been built around 1440, and comprises of a rectangular main tower attached to which was a smaller square wing.

The castle stands on a raised mound jutting out into the Harperrig Reservoir where it is fed by the Water of Leith.

The main tower is three storeys in height, and measures around 8.3 metres by around 7.2 metres, with walls varying from 1.4m to 1.8m in thickness. The ground floor is vaulted and contained the kitchen. An arched doorway gives access to this level.

The secondary tower, the majority of which was removed around 1870, was attached to the south-east corner of the main tower, and measured around 5.5 metres square. It also had a vaulted basement, and there was an intramural spiral staircase close to the re-entrant angle to the north-east. The main entrance to the castle seems to have been a rectangular doorway on the east wall of the first floor.

While the main tower is a substantial ruin, only a lower section of the smaller wing stands. Many of the remaining details, such as the main entrance on the first floor, are now obscured by thick ivy.

Cairns was originally the seat of the Cairns family, with William de Carnys on record in 1349. It’s likely that they had a castle on the land however whether or not it was on the same site is not known.

William’s son, Duncan de Carnys, died around 1390 and was succeeded by his daughter and heiress, Catherine, who had married Stephen Crichton, son of Sir William Crichton of Crichton and Margaret Brunston. Cairns Castle then passed into the Crichton family.

Stephen de Crechtoun was described as “de Carnys” in 1418 and it is his son, George de Crychtoun, to whom the building of the current Cairns Castle is generally attributed in around 1440.

It’s possible that the Crichtons rebuilt an earlier castle in 1440. Certainly the basement of the present castle is older than the rest of it. However it is perhaps more likely that the basement dates from around 1440 and the rest of the castle is later.

George would later be created Earl of Caithness in 1452 by James II. The Cairns estate passed to the Tennent family in the mid-16th century and was the seat of the Tennents of Cairns until 1708.