One of my favorite things to do is take a long walk, primarily because you see many things in the landscape that you might have not noticed previously. The sites might vary for each of us depending on where we live, but when you do stumble upon these secret spaces you can't help but take a moment and smile.
On one of my walks I was following a narrow sidewalk with a brick wall to one side and all of the sudden I had one of those moments which made me stop. There was an opening at eye level that was framed by a raised bed of dark red Lillium (might have been 'Black Bird'), skeletal structure of Allium (onion) bulbs and the limbs and leaves of a Robinia (Locust) tree. Just beyond that initial introduction of greenery there was a sitting area comprised of two chairs and a table, simple and elegant. I found myself wanting to make my way to that sitting area and surround myself with various textures of green on three sides with the backdrop of the common brick wall.
This private garden on its own is fantastic but without that introduction to the space it would have lost some of its charm.
When I begin a design I am always cognoscente of those potential secret spaces that could be created. By varying the architecture of a space and playing with size and proportion, plants can create that secret space. As with most backyards in the city we have a square or rectangle as the blank canvas. Your landscape does not have to reinforce the box shape by only utilizing the exteriors of the space. When you begin to design your landscape it is alright to think outside of that box. Do not be scared to pull and push the plantings away from the walls. Even in small gardens there can be an element of surprise, go for a walk and see for yourself.