The Mourne Wall in Northern Ireland was built between 1904 and 1922 to enclose a reservoir, thus protecting Belfast’s water supply from contamination due to cattle and sheep. The wall is roughly 1.5 meters (5 feet) tall, 1 meter (3 feet) wide and 35 kilometers (22 miles) long. The wall, and Mourne Mountains in general, are located at the southeast edge of Northern Ireland, several miles from the border with The Republic of Ireland. The Mourne Wall climbs the tallest point in Northern Ireland, Slieve Donard at 850 meters (2,788 feet), at the right side of this photo. This photo was taken in spring, when vegetation at the higher elevations was sparse.