At a glance
Rhaeadr Ddu (LL40 2TH) is a free waterfall in Coed Ganllwyd NNR near Ganllwyd on the A470 north of Dolgellau. The "Black Waterfall" cascades through ancient Atlantic oak woodland — free NRW car park in the village. 1 mile walk each way, some steep sections. Outstanding for woodland birdwatching (pied flycatcher, redstart) and lichen/moss interest. Allow 1–2 hours.
About Rhaeadr Ddu
The Afon Gamlan drains the upland bogs of the southern Rhinogau before plunging over Rhaeadr Ddu — the Black Waterfall — and continuing down through the Coed Ganllwyd gorge to join the Afon Mawddach in the valley below. The falls take their name from the characteristic dark colour of the water — stained by dissolved peat and organic matter from the upland bogs above — that turns the cascade near-black against pale rock surfaces in overcast conditions.
The waterfall lies within Coed Ganllwyd National Nature Reserve, one of the finest examples of ancient Atlantic oak woodland in Snowdonia. The same combination of high rainfall, mild temperatures and centuries of undisturbed conditions that make this woodland type exceptional for lichens and bryophytes is what makes it so beautiful to walk through: every surface of rock, bark and branch is clothed in mosses, ferns and grey-green lichen growth of extraordinary delicacy.
In spring and summer, the woodland holds breeding pied flycatchers, redstarts and wood warblers — summer migrants that return from West Africa to nest in the ancient oaks. The Afon Gamlan below the falls holds dippers and grey wagtails year-round. This is a waterfall worth visiting not just for the water but for the habitat that surrounds it.
The walk
- Start — NRW car park, Ganllwyd village, A470 (LL40 2TH). Free parking.
- Distance — Approximately 1 mile to the falls, 1 mile return (2 miles total).
- Ascent — Moderate — some steep and rough sections through the woodland.
- Time — 1–2 hours for the return walk. Take time in the woodland.
- Footwear — Walking boots recommended — the path is uneven and can be wet.
Find it on the map
Frequently asked questions
Rhaeadr Ddu means "Black Waterfall" in Welsh (rhaeadr = waterfall; ddu = black). The name refers to the dark, peat-stained water of the Afon Gamlan, which flows from the upland bogs of the Rhinogau before dropping over the falls. The dark colouration is natural — caused by dissolved tannins from peat and vegetation — and is common in upland Welsh rivers, especially after rain.
Drive to Ganllwyd village on the A470, approximately 5 miles north of Dolgellau. The NRW car park (free, postcode LL40 2TH) is in the village. From the car park, a marked woodland path leads up into Coed Ganllwyd and to the waterfall — approximately 1 mile each way with some steep sections. Allow 1–2 hours return.
Coed Ganllwyd is a National Nature Reserve of ancient Atlantic oak woodland on the steep valley sides above the Afon Gamlan. Like Coedydd Aber near Abergwyngregyn, this is one of the finest examples of the "Celtic rainforest" habitat — ancient oak trees draped in mosses, liverworts and lichens that grow only where centuries of undisturbed, humid conditions prevail. The reserve is of national importance for its lower plant communities, in particular its lichen and bryophyte flora.
Yes — the Coed y Brenin forest (adjacent to Coed Ganllwyd) has an extensive network of walking and mountain biking trails. A popular longer walk takes in Rhaeadr Mawddach (another waterfall on the Afon Mawddach, not to be confused with Aber Mawddach/Rhaeadr Ddu) and returns through different woodland. The Precipice Walk near Dolgellau (5 miles south) is another outstanding option in the same visit.
Coed Ganllwyd is excellent for woodland birdwatching. In spring and summer, pied flycatcher, redstart and wood warbler breed in the oak canopy — the same suite of summer visitors found in similar Atlantic oak woodlands elsewhere in Wales and upland Britain. Dipper and grey wagtail are found on the Afon Gamlan throughout the year. The reserve is also noted for its ferns, mosses and lichens, which carpet every surface in the damp woodland.