What makes this hillfort genuinely odd is that its builders showed no interest in following the shape of the ground beneath them. Most hillforts use the natural contours of a hill to reinforce their defences, but at Rathnagree the three enclosing ramparts push straight across the topography to form three near-circular rings, covering a total footprint of 5.8 hectares. The outermost ring was so faint by the early twentieth century that it did not appear on the 1907 Ordnance Survey six-inch map; today it survives partly as a cropmark visible from the air and partly as a buried feature within commercial forestry. To the west, the slopes drop sharply towards the River Slaney, while roughly 500 metres to the south-east, the much larger Rathcoran hillfort looks down over the whole site.

The name Rathnagree translates from the Irish as 'rath of the king', and the site is one of nine hillforts that make up the Baltinglass hillfort cluster, a concentration of Iron Age and Bronze Age monuments in this part of Wicklow that has attracted archaeological attention for decades. The first modern map depiction of the site appeared in the original Ordnance Survey mapping of 1842. Field surveys followed in 1992 and 1998, and a geophysical survey carried out by O'Driscoll in 2012 produced a particularly revealing result: the low stone banks forming the inner and outer enclosures appeared to be the footings for large timber palisades rather than free-standing walls. Excavation by O'Brien in 2014 confirmed this, and also established a rough date for at least part of the complex. Late Bronze Age coarse ware pottery was recovered from the ditch fill of the middle enclosing element, placing activity at the site somewhere in the later second or early first millennium BC. The middle rampart is the most substantial of the three, an earthen bank averaging 7 metres wide and up to 2.4 metres high, fronted by a ditch of similar width and a counterscarp bank on the far side. The inner rampart, by contrast, is a modest rubble stone bank just 0.2 metres high on average, with no accompanying ditch. Excavation also indicated that the earthen bank and ditch of the middle enclosure was itself built over an earlier palisaded enclosure, suggesting a sequence of construction rather than a single planned event.