Ordnance Survey 1:50,000 scale Landranger map sheet 161 Abergavenny & the Black Mountains Starting from Hay-on-Wye the narrow mountain road climbs steeply to a height of 549 meters Ordnance Survey Map OL13 1:25,000 above sea level, squeezing between the mountains of Twmpa to the west and Hay Bluff to the east, before dropping down into the valley to the south on its way to Llanthony Priory, Llanfihangel Crucorney and Abergavenny.