The most numerous type of prehistoric structure (apart from stone walls) in The Burren is the late-Neolithic/early-Bronze Age wedge tomb, mostly dated to the period 2500 to 2000 BC. It accounts for around 90% of the region's megalithic tombs. Many examples of these are found on Roughan Hill near Kilnaboy, including those at Parknabinnia and Creevagh. Others are located at Gleninsheen and Berneens (Rathborney) and Poulaphuca (Carran). Large stone cairns on many hills, such as the Poulawack Cairn, also date from this period.