The enclosure’s distinctive shape is interrupted along its northern edge, where it appears to have been cut through by a defensive ditch or fosse. These features, visible in Cambridge University aerial photographs from the mid-20th century (specifically images AYM 63 and BDG 82), suggest the remains of a castle complex consisting of a motte and bailey.

The motte and bailey design was a common type of fortification introduced to Ireland by the Anglo-Normans in the late 12th century. These structures typically consisted of a raised earthen mound (the motte) topped with a wooden or stone keep, accompanied by an enclosed courtyard (the bailey) where daily activities took place. The oval shape detected at Dellin likely represents the bailey’s perimeter, whilst the fosse cutting through the northern section would have provided additional defensive capabilities, possibly separating the motte from the bailey or forming part of the outer defences.

This site forms part of County Louth’s rich medieval landscape, documented in both the Archaeological Inventory of County Louth (1986) and the Archaeological Survey of County Louth (1991). Whilst nothing remains visible above ground today, the cropmarks serve as ghostly reminders of the fortification that once stood here, preserving in the soil’s memory what time has erased from the surface.