Ha-ha

Ha-Ha - a trench, with one side vertical, the other gently sloping, a method of containing livestock, which would be invisible from beyond the vertical side.

ha-haA Ha-Ha is a sunk wall with a ditch outside, used so that the garden boundary is not visible from within.

bastion a projecting part of a rampart or other fortification; in landscape gardening, a bastion is a projecting section of the ha-ha.

See also: House, Picturesque, Terrace, Broken, Tower