A ha-ha, also known as a sunk fence, blind fence, ditch and fence, deer wall, or foss, is a recessed landscape design element that creates a vertical barrier while preserving an uninterrupted view of the landscape beyond from the other side. The name comes from viewers' surprise when seeing the construction.
Comparison of a ha-ha (top) and a regular wall (bottom). Both walls prevent access, but one does not block the view looking outward.
Ha-ha at the Hameau de la Reine, Versailles
Ha-ha protecting the lawn at Hopetoun House, West Lothian, Scotland. Note how the wall disappears from view as it curves away to the left of the photograph
Ha-ha and south face of Parham Park, West Sussex, England
The family of Dezallier d'Argenville produced two writers and connoisseurs, father and son, in the course of the 18th century. The father, Antoine-Joseph Dezallier d'Argenville (1680–1765) is now best known for writing the fullest French treatise on the French formal garden style of his lifetime, as well as books on natural history, and as a significant collector of old master prints.
Antoine-Joseph Dezallier d'Argenville.
Opening from the 1712 English edition of The Theory and Practice of Gardening - Wherein is Fully Handled all that Relates to Fine Gardens, Commonly called Pleasure-Gardens, as Parterres, Groves, Bowling-Greens &c. Suggested schemes for gardens of 6 (left) and 12 (right) acres.
