The walls themselves are modest, roughly 0.7 metres thick and just 0.3 metres high where they remain visible, but together they trace a roughly rectangular area of around 350 metres east to west and 200 metres north to south. That a coherent field system of this scale can still be read in the landscape, however partially, is the quietly remarkable thing about Derrygarrane.

Bog growth has a way of preserving what time and agriculture would otherwise have erased. As peat accumulated over centuries, it buried these linear boundaries and held them in place, so that what protrudes today is effectively a cross-section of an earlier, more open landscape when this hillside was worked and subdivided rather than left to rough pasture. What makes the site more than a straightforward field system is what sits within its bounds. A standing stone and a panel of rock art, the latter being prehistoric carvings cut directly into exposed stone surfaces, are both located inside the field boundaries. The co-existence of these elements suggests a landscape that was not only agricultural but carried some ceremonial or symbolic meaning, though exactly how the three components related to one another in use or in time is not something the surviving evidence can settle.