It is easy to overlook entirely; much of its enclosing bank has been worn almost flat by centuries of agricultural activity, and the surrounding landscape shows little obvious sign that anything of age lies beneath the grass. Yet the arrangement of features here rewards closer attention, particularly the relationship between a diminished early medieval enclosure and the more recent field boundaries that have steadily consumed it.

The site is a rath, the Irish term for a roughly circular earthen ringfort, a type of enclosed farmstead typically dating from the early medieval period, between roughly the fifth and twelfth centuries. At Galmoylestown, the enclosure is sub-circular, measuring approximately 22 metres north to south and 20 metres east to west. It was defined by an earthen bank and a wide, deep fosse, the fosse being the external ditch dug to create the bank material and to mark the boundary of the enclosed space. The bank survives in its most recognisable form between the north-east and east-south-east, but elsewhere it has been largely levelled. A narrow entrance gap of about two metres, with a causeway crossing the fosse, sits at the south-south-east. Inside the enclosure, faint traces of cultivation ridges run roughly north-north-east to south-south-west, suggesting the interior was later turned over to tillage. Adjoining the ringfort on its northern side is a small rectangular annexe, roughly six metres by seven metres, enclosed by its own low bank and external fosse. Such annexes are occasionally found at rath sites and may have served as stock enclosures or working yards associated with the main homestead. The eastern side of this annexe has been cut through by a later field bank, which also crosses the main rath's fosse and continues northward, illustrating the gradual way in which working farmland has encroached on and dismantled the monument over time. The townland boundary with Larkinstown lies only ten metres to the west, and the boundary with Down townland has intersected the east-west perimeter of the site, placing the ringfort at the meeting point of three administrative divisions, a coincidence that may itself reflect the site's age and former local significance.