The earthwork at Frenchgrove measures roughly 48 metres along its longer axis, with a scarped edge, where the slope has been deliberately cut away, forming a perimeter that drops to a gentle undulation. The level area at the summit is modest, only around 16 by 10 metres, and the ground slopes gradually from there down to a flattened band near the outer edge. It reads, in other words, like a stage with a frame around it.

The ambiguity is the interesting part. A ringfort, the most common type of early medieval enclosure in Ireland, typically served as a defended farmstead, its circular bank enclosing a domestic space. This enclosure at Frenchgrove could be one; the form is not incompatible. But local information points in a different direction. The rise was once ringed with trees, which were later felled, and the scarp has been partially levelled over time. The more persuasive interpretation is that this was a decorative tree-ring, an ornamental feature laid out on the grounds of Frenchgrove House estate. Such planting schemes were a fairly common element of eighteenth and nineteenth century demesne landscaping in Ireland, designed to create visual interest across open ground. What makes Frenchgrove particularly curious is that a near-identical enclosure sits just 140 metres to the south-west, suggesting the two features were conceived together as part of a deliberate composition across the estate grounds, one whose full logic has since been obscured by the removal of the trees that gave it meaning.