What is a Ha Ha
A ha-ha (or ha-ha wall) is a recessed landscape design element that creates a vertical barrier while preserving views.
The design includes a turfed incline which slopes downward to a sharply vertical face, typically a masonry retaining wall.
Ha-has are used in landscape design to prevent access to a garden, for example by grazing livestock, without obstructing views.
In security design, the element is used to deter vehicular access to a site while minimizing visual obstruction.
The name "ha-ha" derives from the unexpected (i.e., amusing) moment of discovery when, on approach, the recessed wall suddenly becomes visible.