What survives at Killoshulan is a complex of small enclosures, each defined by low earthen banks and accompanying ditches, the kind of landscape feature that is easy to walk past without recognising for what it is: a field system, laid out by people who divided and managed this wet, level ground long before any record was kept of their doing so.

Field systems of this kind are among the less celebrated categories of field monument in Ireland. Unlike a round tower or a high cross, they ask something of the eye. The banks here average around 1.5 metres in width and stand between half a metre and a full metre high, modest enough that seasonal vegetation can obscure them almost entirely. A banked and ditched enclosure typically reflects an effort to both mark a boundary and manage water or livestock, the ditch throwing up the material that forms the bank beside it. In boggy ground such as this, drainage would have been a constant concern, and the layout of small enclosures suggests a careful, incremental organisation of the land rather than any grand single act of construction.