This is a rath, the most common type of early medieval enclosure in Ireland, typically constructed between roughly the fifth and twelfth centuries as a defended farmstead for a single family or small settlement. A rath usually consists of one or more earthen banks thrown up from a dug ditch, or fosse, enclosing a circular or subcircular area where a house and ancillary structures would once have stood. The example at Attidermot is moderately substantial, measuring approximately 48 metres north to south and 45 metres east to west, and retains two banks with an intervening fosse, which places it among the better-defended examples of its type.

The earthwork survives in fair condition, though a field bank has been built on top of the outer bank along much of its western and northern arc, obscuring the original profile on that side. The fosse and outer bank remain more distinct from the east, running through south and back up to the north, where the defensive circuit is easier to read. A gap of roughly 5.5 metres on the eastern side may be the original entrance, the direction that many rath entrances face, possibly for reasons connected with sunrise or prevailing custom. Peter Harbison noted the site in 1975, and it was subsequently recorded in the Archaeological Inventory of County Galway, compiled by Olive Alcock, Kathy de hÓra, and Paul Gosling and published in 1999.