The Llyn Clywedog is a man made reservoir formed by the construction of the Clywedog Dam. The lake has a surface area of 615 acres (230 football pitches), is 216 ft deep at its maximum depth and stretches in all a distance of some six miles.
At its maximum, it is just 500 yards wide. Some 15 miles of new or improved roads were built around the reservoir and a number of viewing points and picnic areas are arranged along the circular drive around the lake enabling visitor to enjoy the wonderful panoramic views.
There is a second, much less visible dam at Bwlch-y-gle. This is an earthen structure faced with stone, about 40ft high and 600ft long which prevents the lake spilling over into the neighbouring valleys on either side of Bryn y Fan hill, the highest of the hills surrounding the lake and a commanding feature to be seen from miles around.
Around the Lake there are a number of walks including the Clywedog Gorge Trail around the Bryn Tail Mine workings and the Llyn Clywedog Scenic Trail.The National Trail of Glyndwr's Way also passes beneath the dam before pursuing a course along the southern shore of the lake.
The Clywedog provides a perfect habitat for wildlife. Buzzards and Red Kite are now a common sight, and recently there have even been occasional sightings of Ospreys. Mallard are attracted to the lake, while Tawney Owls, Pied Flycatchers and a whole host of Tits have established themselves in the woods bordering the shore.
The lake is amply stocked with brown and rainbow trout. The management and fishing rights are the preserve of the Llanidloes Angling Society. Sailing on the lake is run by the Clywedog Sailing Club. Both organisations hold numerous competitions and regattas throughout the year and visitors are always welcome.