The River Urin runs through a deep valley roughly 600 metres to the east, following a northwest to southeast course. This strategic positioning would have provided both defensive advantages and access to water sources for the medieval inhabitants.

The site itself consists of a raised rectangular platform measuring 40 metres from east-northeast to west-southwest and 38 metres from north-northwest to south-southeast. The grass-covered interior sits elevated above the surrounding landscape, enclosed by a straight scarp and an external moat that runs around three sides of the structure. The moat varies in width from 2 to 3.5 metres at its top, with a depth of 1.5 to 2 metres below the interior level. Interestingly, the northern side lacks this defensive moat, instead featuring a laneway that would have served as the primary access point to the site.

These moated sites, common throughout medieval Ireland, typically date from the 13th to 14th centuries and were often associated with Anglo-Norman settlement. They served as fortified farmsteads or manor centres, combining defensive features with agricultural functionality. The Monglass example demonstrates the typical characteristics of these structures; a raised platform surrounded by water-filled ditches that would have supported a timber hall and associated buildings, providing security for both the inhabitants and their livestock during uncertain times.