Rather than a single earthen bank surrounding a central enclosure, as is typical of the most common form of rath, this one at Kilbreanbeg presents a sequence of concentric terraced scarps, three of them, stepping down from a level interior like the rings of a very worn amphitheatre. A rath, to use the Irish term, is an enclosed farmstead of early medieval date, usually from roughly the fifth to the twelfth century, built to protect a household and its livestock. Most are relatively simple in layout. One with multiple concentric enclosures suggests either higher social status or a prolonged period of use and modification, though the historical record here is thin on specifics.

The site sits at the summit of a low hill in pasture land, and at 34 metres in diameter it is a moderately sized example. The inner scarp stands about a metre high and still fully encloses the interior; the intervening and outer scarps are somewhat higher in places, reaching 1.2 metres and 1.1 metres respectively, with level terraced areas of between two and four metres separating them. A stony deposit along part of the inner scarp may be the result of field clearance over the centuries rather than any original feature. The earliest cartographic record comes from the Ordnance Survey six-inch map of 1846, which shows a roughly circular enclosure of around 50 metres in diameter, considerably larger than what survives today. By the time of the 1894 edition, the depicted area had contracted and shifted slightly in outline, suggesting that the outer elements had already suffered significant erosion or agricultural disturbance across that half-century. Surveyors in the 1840s recorded it under the name Kilbreanbeg Fort, placing it in the north-western end of the townland. A second rath lies approximately 250 metres to the west-northwest, on the opposite side of a river, making this a pairing of sites that may once have had some relationship to one another, though what that relationship was remains a matter of speculation.