The problem is that there is no causeway crossing the fosse on the other side. Whatever came and went through that opening, it did so without the benefit of a bridge or a raised crossing, which leaves the question of how the ditch was actually negotiated sitting quietly unanswered.

The site at Ballymongaun is a rath, the most common monument type in the Irish landscape. A rath is a ringfort of earthen construction, typically dating from the early medieval period, roughly the fifth to the twelfth centuries, and used as a defended farmstead for a family of some local standing. This one sits in level pasture and is broadly circular, measuring thirty-five metres on its north-south axis and thirty-three east to west. It is enclosed by an earthen bank that rises to about 1.55 metres on its outer face, with an external fosse, or ditch, around 1.4 metres deep and 1.6 metres wide. The internal height of the bank is considerably lower, at around 0.4 metres, which gives some sense of how much material has slumped or spread over the centuries. A later earthen field boundary, just 0.3 metres high, cuts across the enclosure on a north-west to south-east axis; it continues beyond the enclosure to the south-east but has been removed on the north-west side, suggesting that at some point the agricultural convenience of a straight field line took priority over preserving the older monument intact. The site was recorded by Denis Power and uploaded to the national record in August 2011.

Access would require the permission of the landowner, as the site sits in private agricultural land. The interior is described as marshy and heavily masked by overgrowth, so appropriate footwear matters more than the season, though summer growth will make the interior even harder to read. What is worth looking for, once you have located the bank, is the relationship between the gap and the fosse: standing at that north-north-east opening and looking down into the ditch gives a clearer sense of the original defensive logic than any plan or measurement can.