It is located near to the village of Llanfihangel yn Nhywyn, and is an attractive landscape, with sparkling, blue lakes punctuated by gorse-covered rocky outcrops and distant views of Holyhead Mountain to the north west.

The reserve is made up of a collection of lakes; Llyn Penrhyn, Llyn Dinam, Llyn Treflesg and Llyn Cerrig Bach. Llyn Dinam is a Special Area of Conservation (SAC), and Llyn Cerrig Bach, as well as being noteworthy for its wildlife, is renowned as the find location of Wales’ most important Iron Age treasure hoard.

The nearby reservoir Llyn Traffwll, whilst not forming part of the RSPB reserve, is a SSSI for its plant species and overwintering wildfowl. The lakes collectively support a broad assemblage of birds, including ducks and grebes and wintering coot, teal, wigeon, gadwall and goldeneye. The reserve is one of the last places in Wales where bittern bred, in 1984.

In spring and early summer the reedbeds come alive with reed and sedge warblers, reed bunting, Cetti’s warbler, and water rail. You might be lucky to catch a glimpse of other resident birds like tufted duck and shoveler.

The reserve car park is located off the main road to RAF Valley.

Landscape

Known locally as Anglesey’s mini Lake District, the area is characterised by its scattered, reed fringed lakes and rocky outcrops.

There are three main lakes in the area. Llyn Penrhyn and Llyn Dinam are managed by the RSPB and form part of the Valley Wetlands Nature Reserve. This was the last place on Anglesey where bitterns had been recorded breeding, but this elusive bird can still sometimes be found here especially during the winter months.

During the summer, reed, sedge and Cetti’s warblers can be heard. Llyn Traffwll is the third of the large lakes and has connections to the story of Madam Wen, a local 17th century pirate and smuggler who reputedly hid her treasure in a cave near the water’s edge. Llyn Cerrig Bach is a small lake that forms part of the complex. In 1943 one of the most important collections of Iron Age materials in Western Europe was discovered here. The collection of over 150 items included swords, shield fragments, spearheads and slave chains amongst other artifacts. These were thought to be offerings to Celtic gods between 300 BC – AD 100. To the south of the lakes is Cymyran Bay, a large sandy beach linking Valley Airfield and Tywyn Trewan Common to Traeth Crigyll by the village of Rhosneigr, the surfing capital of the island.