The trail begins at the southern end of the Elan Village beside the River Elan. Walk away from the visitor’s centre and turn right after the cattle grid. Cross the bridge and go through the wooden gate before you (Pic 1). The Trail follows the zig-zag track up through the wood to the top which ends in fine views over the surrounding countryside. Picnic tables have been provided along the way and a series of ten interpretive panels give information on the various tree species and their associated wildlife, birds, mosses, ferns, lichens and fungi (Pic 2).
The wood has been designated as a Site of Special Scientific Interest since 1965 for its richness of lower plants and birdlife. All the wood’s plant and animal life is therefore protected by the law. The oak trees are mostly about 100 years old although some are at least 200. However, Cnwch has been an oakwood for many hundreds of years and is known as an ancient semi-natural woodland – an increasingly rare habitat in Britain. As most of the trees are young in oak tree terms they have few natural holes and crevices for birds to nest in so the Elan Valley’s Countryside Rangers have made up a number of nest boxes to make up for this deficiency. Boxes have been provided for Tawny Owl, Redstart, the smaller species of tit and Spotted Flycatcher, as well as the usual type which is readily taken up by Pied Flycatcher, Great Tit and Nuthatch. The Pied Flycatcher is a common bird here but rare or absent over most of England. The nestling Pied Flycatchers are ringed by the Rangers as part of their broad-leaved woodland research and has also yielded recoveries from Spain, Portugal and North Africa as the birds fly to and from their winter quarters south of the Sahara Desert. There are also some bat boxes down by the river which have a slit in the bottom instead of a hole.
In the Summer many insects eat the oak leaves. Moth caterpillars, in particular, completely strip the trees in some years despite nearly every bird feasting on them. The oak has a second flush of growth during July and August partly to compensate for the eaves lost to these larvae. This growth is very conspicuous as the leaves area light green or reddish and almost translucent for a time. This is called the Lammas growth -0 an ancient name associated with Lammas Day, the first of August. This was once a harvest festival, Lamaas being derived from the old English word meaning ‘bread-feast’
Most of the rocks in the area of Cnwch were formed more than 400 million years ago when Wales was under an ocean. They are mainly slates and shales but you may find some large pebbles along the track in a few places, the same as you would by a seaside, indicating the once maritime environment. There are very few fossils in the rocks, only the occasional grapolite – a small narrow, feather-like sea animal. Along the track beyond the ‘birdlife’ and ‘birch’ panels a small detour from the trail takes you to Caban Coch Dam. Beyond this the track becomes narrow and rocky along the reservoir shore. About half way up the zig-zag track there is a small stone building up to the right. This is where explosives were stored during the building of the dams and reservoirs – away from the works, people and houses. The track itself was made to bring sheep down from the hills to the south of the Claerwen Valley as when the area was flooded the old tracks were submerged.
Toward the top of the trail the water treatment works can be seen across the valley. The series of filter beds remove fine particles of peat before the water continues its 70mile journey to Birmingham. From the very top, by the final interpretive panel, there are fine views down the wooded Afon Dulas valley and across to Carn Gafallt – scene of one of the legends of King Arthur described in ‘The Mabinogion’.