OSNILandranger 29, OSNI Outdoor Pursuits map Mourne Country
Slieve Binnian (from the Irish: Sliabh Binneáin) is the third highest mountain in Northern Ireland at 747 metres (2,451 ft). The name comes from the rocky tors situated around the top of the mountain. These very rugged crest of rocky tors makes it easy to identify in views around the Mourne Mountains.
The Binnian Tunnel was built in the late 1940s underneath Slieve Binnian, to transport water from the Annalong Valley to the Silent Valley. It took four years to construct, and two tunnelling teams started from opposite ends and met in the middle. Having been carefully measuring their positions the whole time, they found they were only two inches off course when the two tunnels met.