The nature reserve is a 2.5km stretch of dramatic wooded limestone gorge cut by the River Taf Fechan, between the bridges of Pontsarn and Cefn Coed to the North of Merthyr Tydfil.
It lies adjacent to the eastern side of the popular Taff Trail. and the reserve incorporates much of the area notified as Cwm Taf Fechan Woodlands Site of Special Scientific Interest.
The reserve has high nature conservation value and supports uncommon flora and fauna.
On the western bank of the river you can see a good population of broad leaved helleborine, as well as small-leaved lime. In addition, there are large areas of grazed limestone grassland, some with bracken, with plentiful violets providing a suitable habitiat for silver-washed fritillary butterflies.
The Eastern bank sees a number of springs, with Tufa deposits, and the Gurnos quarry face is well developed, with facies and caves likely to be home to bats.
The reserve has a wide diversity of habitats, fast and slow flowing fresh water, open and dense deciduous woodland; calcereous and acidic grassland; exposed limestone cliff faces and old walls and tufa springs.
Signs of otters are regularly spotted, and the whole river stretch supports birds such as dipper and grey wagtail. Goosander are regular in Winter, and evidence of badgers are often seen.
The gorge was created by the young Taf Fechan river cutting into the northern outcrop of carboniferous limestone, forming the northern border of the south Wales coalfield.
A particularly impressive section is to the east of the Trefechan estate. The geology is especially obvious in the Gurnos quarry.
South of the quarry, millstone grit is the underlying rock. At the site of the Heads of the Valleys road bridge there are fallen blocks of honeycomb sandstone, the marker horizon which occurs at the S zone / D zone boundary in the carboniferous limestone over a wide area of the north crop of the coalfield.
The sandstone outcrops at the top of the vertical face south of the Gurnos quarry cliff. The majority of the site, to the north of the road bridge, consists of the Cil yr Ychen series of carboniferous limestone. This is richly fossiliferous, with brachiopods (typically seminula), productids, corals and gastropods (including Euomphalus).
The Pont Sarn bridge by the Blue Pool (Pont-sarn-hir - the bridge of the long paved road) is the site of the roman road crossing, travelling from Y Gaer at Brecon to the coastal fort at Cardiff. From the bridge it went through Gurnos, towards Penydarren Park and on to Gelligaer.
There are the remains of an eighteenth century corn mill on the eastern bank of the northernmost section of the reserve, one of four grinding mills that were located in the Taf Fechan valley. The original millstone grit millstone is nearby.
Further down the river are the remains of a fullers mill (a pandy) on western bank just north of timber bridge. Well-known local weavers, the Harris family, owned both these mills.
The Gurnos quarry supplied limestone for the furnaces of the Cyfarthfa Ironworks. Following the closure of the Ironworks, the quarry was planted with a selection of pine trees, with some still surviving on top of the cliff.
The tramway runs south from the quarry alongside the Taff, to beyond the Cefn Coed bridge. It was extended to reach the new Glamorganshire canal in 1792. It supplied the Cyfarthfa Ironworks with the all important limestone needed for the ironworking process, and the stones forming the base of the tramway rails are a scheduled ancient monument, as is the Cyfarthfa leat which runs alongside it.
Penmoelallt Community Woodland is managed jointly by the Merthyr Tydfil & District Naturalists Society and Natural Resources Wales.
The area is a natural Limestone woodland of particular omportance due to the presence of an extremely rare species of Whitebeam. Ley’s Whitebeam, Sorbus leyana is only found in one other site. This species can be found on the ledges and cliff areas of the site, along with 10 metre specimens of Sorbus rupicola. This site is a site of Special Scientific Interest. (SSI)
The woodland can be accessed from the A470, on the outskirts of Cefn Coed.
Cilsanws Nature Reserve is owned by the Merthyr & District Naturalists Society and is completely open for you to explore and enjoy.
There are a few ways to access the area, situated on the south western side of Cilsanws Mountain.
By travelling through the village of Cefn Coed, heading towards Trefechan, you can access the reserve via Cloth Hall Lane and Merthyr Tydfil Golf Course Car Park.
Larches and Scots Pine grow along the Western margins of the reserve, with more unusual rowan or mountain ash trees springing up on the higher ground. The Rowans attract species such as thrush, starlings and blackbirds, and swifts, swallows, house-martins, buzzards and kestrels are commonly present.
If you are lucky, you may catch a glimpse of a rare peregrine falcon flying by.
Mammals are shy but are present - field mice, bank voles and common shrews live in the reserve and there are an abundance of insects and butterflies, so important to the balance of the reserve.
Despite at first glance appearing deserted there is more to Gelligaer than meets the eye – its complex history of fact and legend has left interesting Roman and Medieval remains. Among its gems are a interesting Roman and Medieval remains. Among its gem are a megalithic burial mound at Carn Bugail, the Cen Gelligaer Stone and the remnants of Capel Gwladys, the mother of Tydfil the Martyr from which Merthyr Tydfil gets its name.
On the outskirts of Gethin Woodland Park lies the reserve of Webber's Pond. Webbers Pond is owned and managed by the Merthyr Tydfil & District Naturalists Society.
During Spring and Summer, the pond teems with life - dragonflies, amphibians and wild flowers are in abundance. Bird watchers can see warblers, finches, woodpeckers and kingfishers. In winter, redpoll and siskin can be seen in the area.
Child friendly dipping platforms and fishing areas make the area great for a day out for the family, and parking can be accessed nearby by following the turning for Gethin from the A470 in Merthyr Tydfil.
The woodland is managed by the Forestry Commission who strive to protect the under threat rhos pasture (rough and marshy grassland).
Gethin Woodland is the site of exciting future Mountain Biking developments which will enable you to access Webbers Pond on two wheels rather than four by the end of 2013.
This area was once part of Gethin Colliery which was owned by the Cyfarthfa Iron Company. The pond was built to provide water to the Gethin Pit No 2 with its own pond keepers house.