| Slieve Binnian | |
| Other Name: | Sliabh Binneáin |
| Elevation M: | 746 |
| Prominence M: | 349 |
| Listing: | Marilyn, Hewitt |
| Location: | County Down, Northern Ireland |
| Range: | Mourne Mountains |
| Grid Ref Ireland: | J320234 |
| Topo: | OSNI Landranger 29, OSNI Outdoor Pursuits map Mourne Country |
Slieve Binnian [1] is one of the Mourne Mountains in County Down, Northern Ireland, 9 km north of Kilkeel. It is the third-highest mountain in Northern Ireland at 747m (2,451feet). The summit is broad and flat with rocky tors at the north and south ends, with the Back Castles, impressive towers of granite, in between.[2] [3] To the south-west is Wee Binnian (460m).[1] It lies east of Silent Valley Reservoir and west of the Annalong Valley. The Mourne Wall also crosses over Slieve Binnian.[2]
The mountain is in the townland of Brackenagh East Upper (379 acres), the civil parish of Kilkeel and the historic barony of Mourne.[1] [4]
The Binnian Tunnel (2.5 miles long) was built between 1947 and 1950/51 underneath Slieve Binnian, to transport water from the Annalong Valley to the Silent Valley. A workforce of 150 was involved in two tunnelling teams which started from opposite ends and met in the middle nearly 800m under the roof of the mountain. Having been carefully measuring their positions the whole time, they found they were only two inches off course when the two tunnels met.[3] [5]