First recorded on Ordnance Survey maps in 1837 and again in 1914, this circular earthwork enclosure measures approximately 40 metres across its exterior diameter. The site consists of a rectangular grass-covered central area, roughly 33 metres from east to west and 31 metres north to south, bordered by various earthen features that have survived the centuries.

The southern edge is defined by a scarp about one metre high, whilst the northern boundary follows an existing field bank. The western and eastern sides feature substantial earthen banks; the western bank measures 2.7 metres wide with an interior height of 0.4 metres and exterior height of 0.6 metres, whilst its eastern counterpart spans 3.45 metres in width with slightly lower heights of 0.3 metres internally and 0.65 metres externally. What makes this site particularly interesting is the presence of an outer fosse, or moat, along the western side. This defensive ditch has a base width of 6.75 metres, though it’s now only about 0.25 metres deep, with an accompanying outer bank that’s 3 metres wide and stands 0.25 metres high.

About 80 metres to the northwest lies another rath, catalogued as RO011-111001, suggesting this area held strategic or settlement importance in medieval times. These moated sites, typically dating from the Anglo-Norman period, were often associated with manorial settlements or defensive homesteads. The preservation of the earthworks at Grange offers a tangible connection to the medieval landscape of Roscommon, where such fortified enclosures served both practical defensive purposes and as symbols of authority in the Irish countryside.