Silent Valley Reservoir

Silent Valley Reservoir, in the heart of the Mourne Mountains, supplies drinking water to much of County Down and part of Belfast. The earth-and-rock dam holds back the Kilkeel River and was built between 1923 and 1933. Further up the valley, the Ben Crom Reservoir was created between 1953 and 1957 with a concrete dam. The catchment is enclosed by the Mourne Wall, a granite dry-stone wall built between 1904 and 1922 to keep livestock out of the water catchment. It crosses some 15 summits; sources give its length as anywhere from 19.5 to 22 miles (about 31 to 35 km).

The entrance is on Head Road near Kilkeel, and the large car park at the southern end is charged. There is also an information centre. NI Water describes several trails, including a nature trail (1.8 km) along the Kilkeel River and the old railway line, and the tarmac road to Ben Crom (10 km return). Some trails may be closed for repairs, so check beforehand. Be prepared for rain.