|A view across Bodnant Garden to the mountains beyond|
The trick is to use something within the garden to draw the eye towards something beyond the garden boundary. This has the effect of joining the two in the mind of the viewer. Sometimes this makes it feel as if the distant object is part of the garden. At the very least it extends the reach of the garden when looking at it, and avoids the feeling of confinement that you can experience in a limited space.
The above picture was taken on the terrace at Bodnant Garden in North Wales. From this raised position, you look down on the lawn and pond, but the rill directs your eye outwards, towards the pool. The circular far edge of the pool further leads the eye towards the far side of the lawn, where the low balustrade serves as a false horizon. Beyond this the ground drops away, and so from this vantage point this would appear to be the end of the garden. But the eye naturally wanders on, to the trees and mountains beyond, so that the view is effectively infinite, regardless of the point at which the garden you are in actually finishes. The view is virtually uninterrupted. The balustrade is low and unintrusive, compared to a high wall, dense hedge or solid structure.
From the bottom of my garden, the top of the conical towers of Castell Coch are visible (much more so than it appears from this photo!). In line with the seating area and the castle towers I have planted a cone shaped conifer, so that when looking along that line the conifer points towards the towers and echoes their shape. This tends to lead the eye up and out of the garden, rather than simply towards the back of the house. Another conifer slightly further up has two main stems and has been cut to form two more pointed tips, also echoing the towers' shape. This is a simple and inexpensive device that demonstrates how you can influence the direction of the eye by either pointing to, or framing, something beyond the boundary, helping to use distant views to make your garden feel slightly larger than it is.