At Coonagh West in County Limerick, one such structure was uncovered during excavations for the Southern Limerick Ring Road, Phase II, and what emerged from the alluvium told a layered story of a landscape used, abandoned, and reoccupied across thousands of years.

The causeway was built from a dry glacial ridge, pushing south-westward through marshy terrain for almost 67 metres in the direction of the Shannon, which lies roughly 700 metres to the north. Where it met the gravel ridge at its northern end, the structure was a substantial 8 metres wide; further along, it narrowed considerably, to around 0.8 metres across and between 0.2 and 0.4 metres deep. It was well constructed, with larger kerb stones forming the edges and a prepared walking surface laid between them. Excavations directed by Taylor in 2004 and 2005 established that the causeway sat on top of alluvium, the river-deposited sediment that built up over time, which distinguished it from an older prehistoric trackway found just 40 to 80 metres to the west. That earlier trackway predates the causeway, and both may have been aimed at reaching the same stream. The causeway itself is considered contemporary with a ringfort, a roughly circular enclosure typical of early medieval Ireland, located just 60 metres to the north on the same ridge. Nearby, excavators also found two Bronze Age round buildings and two fulacht fia sites, the latter being ancient cooking places, typically consisting of a hearth, a water trough, and a mound of fire-cracked stone, found across Ireland in considerable numbers.

The site is not publicly accessible in any formal sense, having been excavated as part of road construction works, and much of the landscape here has since been altered by development. The records held through excavations.ie, particularly Site No. 975, offer the most detailed publicly available account of what was found. For those researching the early medieval and prehistoric settlement of the Shannon estuary corridor, the excavation reports by Taylor and the broader Bermingham et al. synthesis from 2013 are the most useful starting points.