The defining feature of this medieval earthwork is its surrounding bank, which varies considerably in size around the perimeter. Along the northern and southern sides, the bank is quite substantial, with a base width of 5.5 to 7 metres, rising between 0.3 and 0.6 metres on the interior side and reaching 0.9 to 1.4 metres in height when viewed from the outside. The western bank is noticeably smaller, with a base width of just 3.2 metres and a height of only 0.3 metres, whilst the eastern side lacks a bank entirely.

What makes this site particularly interesting is its outer defensive ditch or moat, which doesn’t follow the expected pattern of completely encircling the interior. The northern and southern sections feature a fosse that’s 6 metres wide at the top with an external depth ranging from 0.1 to 0.3 metres; rather shallow for a defensive feature. The western side has no trace of this outer ditch at all, whilst the eastern side, despite having no bank, actually has a more substantial moat measuring 4 metres wide at the top.

These moated sites were typically constructed during the Anglo-Norman period in Ireland, serving as fortified homesteads for colonising families. The irregular nature of Portan’s defences, with varying bank heights and an incomplete moat system, might indicate different phases of construction or perhaps that the site was never fully completed. Such earthworks offer valuable insights into medieval settlement patterns in the Irish midlands, where the Anglo-Norman influence met and merged with existing Gaelic traditions.