At Mullaghreelan in County Kildare, two ancient trackways lie almost entirely invisible to anyone walking the land above them. They survive not as raised banks or worn hollows, but as cropmarks, subtle variations in the growth of vegetation that appear only when viewed from the air under the right conditions. Aerial photographs taken as part of the Cambridge University Collection of Aerial Photography, reference CUCAP BGN 36, revealed the outlines of two pairs of fosses, that is, ditches or earthen channels, which once defined two approximately parallel routes running east to west and spaced roughly 150 metres apart.

Cropmarks form when buried features affect how crops or grasses absorb moisture and nutrients, causing them to grow taller or shorter than the surrounding vegetation, and under the right light and season they become legible from altitude in a way they never are from the ground. Here, the southern of the two trackways can be traced leading westward from a wooded area towards a square-shaped field that archaeologists have identified as a possible moated site, recorded separately in the national monuments register. A moated site, a feature associated broadly with the medieval period in Ireland, typically consists of a rectangular or square enclosure surrounded by a water-filled ditch, often serving as a defended farmstead or minor manorial centre. The estimated maximum length of the southern trackway runs to around 280 metres. Whether the two routes were in use simultaneously, or belong to different phases of activity at the site, is not something the aerial evidence alone can resolve.