Within a radius of roughly 150 metres, this worn circular earthwork sits alongside at least two other ancient enclosures, a density of early medieval settlement that suggests this quiet stretch of County Galway was once considerably busier than it appears today.

The site is a rath, the most common type of ringfort in Ireland, typically constructed as a circular farmstead enclosed by an earthen bank and an outer ditch, known as a fosse, during the early medieval period, roughly between the fifth and twelfth centuries. At Knockogonnell, both features survive, though only just. The bank has been significantly reduced over time, and the fosse, which would originally have run around the full perimeter, now exists only along the northern arc. The internal diameter of the enclosure measures 30.8 metres, placing it within the typical range for a single-family farming settlement. Neighbouring it to the east, approximately 130 metres away, is a second ringfort, and to the south-south-east, around 150 metres distant, lies a further enclosure of uncertain character. The three sites together hint at a small community or a succession of occupation across the same landscape over generations.

The earthwork sits in grassland, which at least keeps the outline legible at ground level, even if centuries of agricultural use have softened what was once a more pronounced form. The northern fosse is the detail most worth locating; it is the one fragment where the original intention of the design remains tangible.