Wall - Boundary Walls

Boundary Walls

Boundary walls include privacy walls, boundary-marking walls on property, and town walls. These intergrade into fences; the conventional differentiation is that a fence is of minimal thickness and often is open in nature, while a wall is usually more than a nominal thickness and is completely closed, or opaque. More to the point, if an exterior structure is made of wood or wire, it is generally referred to as a fence, while if it is made of masonry, it is considered a wall. A common term for both is barrier, convenient if it is partly a wall and partly a fence, for example the Berlin Wall. Another kind of wall/fence ambiguity is the ha-ha which is set below ground level, so as not to interrupt a view yet acting as a barrier to cattle for example.

Before the invention of artillery, many of the world's cities and towns, particularly in Europe and Asia, had protective walls (also called town walls or city walls). In fact, the English word "wall" is derived from Latin vallum, which was a type of fortification wall. Since they are no longer relevant for defense, such cities have grown beyond their walls, and many of the walls, or portions thereof, have been torn down, for example in Rome, Italy and in Beijing, China. Examples of protective walls on a much larger scale include the Great Wall of China and Hadrian's Wall.