"looking over a ha-ha into the park"
Ha-ha at Lydiard Park, Swindon
Creative Commons Attribution Share AlikeHa-ha at Lydiard Park, Swindon - Credit: Brian Robert Marshall

 In garden design, a  ha-ha is a concealed trench whose purpose is to create a barrier, usually to keep livestock out, while at the same time allowing an unobstructed view from a garden or park. It also refers to the type of ditch sometimes known as a deer-leap, one side of which is vertical and lined with brick or stone.