The spectacular drystone Mourne Wall marches across the summits of 15 surrounding peaks, including the highest, Slieve Donard (853m). You can walk the 2m-high, 1m-thick, 35km-long wall's entire length, or just a short section.
Although the 1922 wall was built to stop livestock reaching the catchment area of the Rivers Kilkeel and Annalong, poor geological conditions meant the Annalong couldn't be dammed, and its waters were diverted to the Silent Valley Reservoir via a 3.6km tunnel beneath Slieve Binnian.