Enjoy a nice circular walk around this beautiful lake in the Snowdonia National Park. You can start the walk from the Llyn Dinas car park at the western end of the lake, off the A498. It's about 1.5 miles east of Beddgelert. From the car park pick up the public footpaths heading above the south eastern side of the water. There's some moderate climbing as you head through the woodland above the reservoir. The path eventually takes you to the end of the reservoir where you can cross the Afon Glaslyn and return along the road to the car park. Alternatively you can return the same way through the woods and avoid the road.
To continue your walking in the area you could visit the beautiful Aberglaslyn Pass near Beddgelert. Also nearby are miles of cycling and walking trails in Beddgelert Forest.
Along the Afon Glaslyn you will find Llyn Gwynant which has some nice footpaths along the water and through the surrounding woodland.