The main cairn on top of Knockma is huge, easily up there in size with Queen Maeves Cairn on Knocknaree.
Its very difficult to see with the trees around it and does call into question how some hill-top cairns would have been visible if foliage began to encroach.
Its also a welcome change from having to climb over ditches and rivers as there is a path all the way up to the cairn. There is a parking area on the north side of the hill and the walk up to it seems to very well used.
Although funnily enough the cairns themselves arent easily viewed from the path. So either you need to go up here when the trees dont have leaves or else bring a GPS.
There are amazing views to the south and west with many interesting mountain ranges.
There is a second smaller cairn which seems to have been modified into a defensive structure.