The raised area measures roughly 23.8 metres north to south and 22 metres east to west, defined by an earthen bank and encircled by an external fosse, a shallow defensive ditch that now shows as little more than a surface depression in the grass. Stones push up through the top of the bank in places, hinting at earlier construction beneath the turf. The bank survives unevenly, standing just 0.2 metres above the interior on the north-west side and rising to 0.65 metres at the south-east. There is no clearly defined entrance, though a narrow eroded break of about 0.6 metres cuts through the south-west of the bank.

This is a rath, the most common type of early medieval settlement monument in Ireland, typically dating from roughly the sixth to the twelfth century. A rath is essentially a single-family farmstead enclosed by one or more earthen banks and ditches, used to define territory, provide modest security, and signal social status. The Tooreen example is unassuming in scale but well-positioned: from its terrace the ground opens to views south and west over rolling pasture, and north over the flat estuarine lands at the southern end of Lackan Bay, a wide inlet on the north Mayo coast. That northward prospect over the estuary would have made the site a useful vantage point, whatever its primary function. Inside the enclosure the ground is level, apart from a small grass-covered mound, roughly two metres across and 0.3 metres high, sitting slightly east of centre. This is most likely a field clearance heap, the accumulated result of stones being gathered and piled during later agricultural use of the interior, rather than any original feature of the site.