Double Sided Walls
Double sided walls have many possibilities.
They can be a natural guardrail along the driveway, a low rubble wall at the edge of one's property or my favorite, a section at the edge of a patio to park your bottom for a short rest.
They can also incorporate lighting, or be part of a water feature, as a wall for water to come from.
In the example below, you will notice a wall in progress where a conduit is installed for lighting that would come later in the project.