On the southern bank of the Ferta river near Toon, a series of pre-bog field boundaries, walls that were already ancient before the bog grew over them, extends across an area roughly 350 metres north to south and 200 metres east to west. The Deelis-Teeromoyle road cuts straight through the middle of it, which gives the whole complex an oddly bisected quality, one half of an old agricultural world on either side of a modern road.

The walls themselves are a mixture of forms: some curvilinear, some angular, most low and collapsed, others still standing as rows of upright slabs. The longest surviving stretch runs for around 260 metres along the north-western edge of the complex, though it dips in and out of the peat rather than holding a continuous line. What makes the site particularly telling is the evidence from excavated drains and trackways through the bog. These cuttings have revealed that several walls are founded directly on the pre-peat mineral soil, which now sits at an average depth of 1.3 metres below the bog surface. In other words, at the time the walls were built, this was open, workable ground, farmed or divided in ways that suggest an organised agricultural presence well before the bog claimed it. Approximately 45 metres to the west of the complex, a possible standing stone, rectangular in profile, reaching 1.25 metres in height and oriented north-east to south-west, may be a further remnant of the same pre-bog period, though its precise relationship to the field system remains uncertain.