Along the garden-wall the bees All are architects of Fate,

With hairy bellies pass between Working in these walls of Time;

The staminate and pistillate, Some with massive deeds and great,

Blest office of the epicene. Some with ornaments of rhyme.

- T.S. Eliot - Henry Wadsworth Longfellow

Flower in the crannied wall,                                Cooling, so cooling,
I pluck you out of the crannies,                               with a wall against my feet,
I hold you here, root and all, in my hand,                      midday sleep—behold.
Little flower—but if I could understand                     - Matsuo Basho
What you are, root and all, and all in all,
I should know what God and man is.
- Alfred Tennyson

When one family builds a wall, two families benefit from it.
- Chinese Proverb

“A cat improves the garden wall in sunshine, and the hearth in foul weather.”

- Judith Merkle Riley

In the garden the door is always open into the holy.
- May Sarton

Earth’s crammed with heaven, and every common bush afire with God:
But only he who sees takes off his shoes.
- Elizabeth Barret Browning

Even in a single leaf of a tree, or a tender blade of grass,
the awe-inspiring Deity manifests Itself.
- Shinto. Urabe-no-Kanekuni

Almost any garden, if you see it at just the right moment,
can be confused with paradise.
- Henry Mitchell

Walls can be used for a number of different purposes in a garden.

Building terraces to allow more efficient and effective gardening of a slope
Creating vertical space - using 3 dimensions in the garden space
Defining space both vertically and horizontally
As garden features in and of themselves

Wall materials vary widely in both the cost of the material and the cost of construction. They can be made to have dramatically different "looks" and "feels". It is a rare garden that won't benefit from some well-designed wall and terrace work.

The three photos below show a front yard that was transformed from bluegrass to garden, using a natural granite stone to create terraces. Note that as the garden matures over the first 12 months or so, the stone walls are absorbed into the garden, and become more and more integrated with the garden as it develops. The first photo is soon after planting, the second photo is later that same summer, and the third photo is the second year.