rise of the woollen industry. Access The Glyderau present a much more rocky appearance than the smooth rounded humps of the Carneddau just to the north. The ridge between the summits of Glyder Fawr and Glyder Fach is covered with coarse grasses and heathers and strewn with boulders and slabs of rocks. The ascent to the summit of Tryfan requires scrambling rather than just walking. Tryfan, Glyder Fach and the cliffs around Cwm Idwal offer rock climbing with routes ranging from those suitable for beginners to those requiring great technical expertise. The mountains can be approached from Llyn Ogwen to the north, where there is a car park, or from Nant Peris in the Llanberis Pass where there is a park and ride service. Buses run hourly from Bangor to Llanberis and there is a less frequent service from Bethesda to Llyn Ogwen. Cwm Idwal The north-facing amphitheatre-shaped valley of Cwm Idwal with its dark cliffs has a unique flora, and some plants here are the most southerly remnants in Britain of the Arctic/Alpine flora. The Snowdon lily (Lloydia serotina) is found here, high on mountain ledges, the only place in Britain where it is found. Other Alpine species include the purple saxifrage (Saxifraga oppositifolia), tufted saxifrage (Saxifraga cespitosa), Alpine meadow rue (Thalictrum alpinum) and mountain sorrel (Oxyria digyna). Because of the scientific interest of this valley, sheep have been excluded from it to allow the native plants to flourish and it has been made into a national nature reserve. The lake itself is shallow and fringed with rushes, reeds and bottle sedge (Carex rostrata). Plants growing in the water or on the damp ground nearby include awlwort, pillwort, waterwort and spring quillwort (Isoetes echinospora). Other plants growing on damp shady ledges include the Welsh poppy (Meconopsis cambrica), the wood-rush (Lazula sylvatica), water avens (Geum rivale), wood anemone (Anemone nemorosa) and goldenrod (Solidago virgaurea). Animals that live here include badgers, foxes and polecats as well as buzzards (Buteo buteo), peregrine falcons (Falco peregrinus), choughs (Pyrrhocorax pyrrhocorax), skylarks (Alauda arvensis), black grouse (Tetrao tetrix) and red grouse (Lagopus lagopus). In the cliffs above Llyn Idwal is a dark cleft in the rock known as Twll Du from which plumes of mist sometimes emanate. These were believed to be caused by ancient druids creating lightning bolts to keep the invading Romans at bay. Llyn Idwal itself was said to be named after