The Mawddach Estuary is a striking sight, flanked by woodlands, wetlands and the mountains of southern Snowdonia. There are two Royal Society for the Protection of Birds (RSPB) nature reserves in the valley, both easily reached on foot or by bike from Dolgellau or Barmouth via the Mawddach Trail. Arthog Bog is 8 miles west of Dolgellau on the access road to Morfa Mawddach station, off the A493, while Coed Garth Gell is 2 miles west, on the A496.
On the south side, Arthog Bog is a small wetland reserve favoured by cuckoos, grasshopper warblers, lesser redpolls, reed buntings and siskins. Set in oak woodlands along the northern side, Coed Garth Gell has two circular walking trails; one 1.25 miles, the other 1.5 miles. Spring visitors include redstarts, wood warblers and pied flycatchers, while in summer you might spot dippers and, in winter, woodcocks.