The Mourne Wall is a stone wall located in the Mourne Mountains of Northern Ireland. It was built between 1904 and 1922 to enclose the Mourne area, which is a designated water catchment for the Belfast Water Works. The wall stretches approximately 22 miles and includes 15 mountain summits. Constructed primarily from local granite, the wall stands as a significant engineering feat and a popular hiking destination. It serves both practical and aesthetic purposes, providing a boundary for the water supply while also enhancing the natural beauty of the surrounding landscape.