The Ha-Ha wall is an interesting type of wall. Ha-Ha's were introduced to the UK from France by Capability Brown and belong to the landscape garden style of the 18th century.
A Ha-Ha is a boundary barrier that does not block the view. It was used to keep animals such as sheep and cattle out of the formal garden without losing the view across the countryside. a Ha-Ha was usually a 'semi-ditch' with the garden side a wall.
Hunterston has two Ha-Ha walls, both are located at the mansion house, one located at the front and one at the back.