Perched on the northern shoulder of a hill some 300 metres from the impressive Rathgall hillfort, Knockeen stands as one of County Wicklow's most intriguing ancient monuments. This circular hillfort, with a maximum diameter of around 200 metres, cleverly follows the natural contours of the hilltop whilst taking full advantage of the steep northern slopes for defence. What remains of the earthen and stone bank reaches heights of 1.5 metres and widths of 5 metres, though much of the northern and eastern sections have been lost to time. At its centre sits a large cairn, from which two ancient fence lines once radiated outward; these were noted by antiquarian George Henry Orpen in 1911 as being of remarkable size and possibly ancient origin.

Recent archaeological investigations have revealed that Knockeen is far more complex than surface remains suggest. Aerial photography from Cambridge University and geophysical surveys conducted in 2014 have confirmed this to be a bivallate hillfort, featuring two concentric rings of defences separated by approximately 50 metres. The outer rampart, whilst largely destroyed by modern roads and farm buildings, can still be traced as cropmarks in aerial photographs, particularly visible along the southern, southwestern and western sections. The total site footprint encompasses an impressive 6.2 hectares, making it a substantial defensive position in the prehistoric landscape.

Perhaps most fascinating are the discoveries made within the interior through geophysical survey. Up to twenty possible hut structures have been identified, along with evidence of pits and what appear to be relict field systems, painting a picture of a once thriving community. The survey also confirmed the presence of an infilled external ditch accompanying the inner bank, a defensive feature not visible on the surface today. These findings suggest Knockeen wasn't merely a refuge in times of danger but likely served as a permanent settlement where daily life unfolded within its protective embrace. The site's proximity to Rathgall hillfort hints at a broader network of hilltop settlements that once dominated this corner of Wicklow, each commanding sweeping views across the surrounding landscape.