Llyn Llywenan is a lake in western Anglesey

Anglesey

Anglesey , also known by its Welsh name Ynys Môn , is an island and, as Isle of Anglesey, a county off the north west coast of Wales...

, Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 found just over 1 kilometre (0.621372736649807 mi) north of the village of Bodedern

Bodedern

Bodedern is a village in the west of Anglesey, North Wales, at . The Royal Mail postcode begins LL65. The population was 1,017 in 1991.The village has a fully bilingual secondary school, Ysgol Uwchradd Bodedern and a football team, Bodedern Athletic F.C. who play in the Welsh Alliance League...

 and 9 kilometres (5.6 mi) east of the town of Holyhead

Holyhead

Holyhead is the largest town in the county of Anglesey in the North Wales. It is also a major port adjacent to the Irish Sea serving Ireland....

. At a maximum length of 1.1 kilometre (0.683510010314787 mi) and breath of 0.4 kilometre (0.248549094659923 mi) it has a surface area of only 0.4 square kilometre (0.154440863437014 sq mi). This makes it the largest natural lake on the island—both Llyn Alaw

Llyn Alaw

Llyn Alaw is a man-made reservoir on Anglesey, North Wales. It is used to supply drinking water to the northern half of the island and does so at a rate of 35 million litres a day. It was created in 1966 on existing marshland....

 and Llyn Cefni

Llyn Cefni

Llyn Cefni is a small reservoir in the centre of Anglesey, Wales which is managed by Welsh Water and Hamdden Ltd. It is located just one kilometre north of the island's county town of Llangefni and is the source of the Afon Cefni and other smaller watercourses...

 are larger but are man made.

The lake, a Site of Special Scientific Interest

Site of Special Scientific Interest

A Site of Special Scientific Interest is a conservation designation denoting a protected area in the United Kingdom. SSSIs are the basic building block of site-based nature conservation legislation and most other legal nature/geological conservation designations in Great Britain are based upon...

, is situated 34 metres (111.5 ft) above mean sea level and was chosen as an SSSI as there are uncommon aquatic plants there, as well as the fact that the lake is very shallow and could in the next hundred years or so be filled with silt

Silt

Silt is granular material of a size somewhere between sand and clay whose mineral origin is quartz and feldspar. Silt may occur as a soil or as suspended sediment in a surface water body...

. There is a small, rather featureless, island in the middle of the southern section of the lake which is roughly 35 metres (115 ft) across.

There are two neolithic

Neolithic

The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...

 burial mounds immediately to the south of the lake, one of which is quite complete. The character Lord Owen Griffiths for the American role playing game Castle Falkenstein

Castle Falkenstein

Falkenstein Castle or Castrum Pfronten is a High Middle Ages castle ruin in the Bavarian Alps, near Pfronten, a town in southern Germany. The ruin's German name is Burg Falkenstein...

has a lover Gwagged Annwn Nimüe who, in the game world, lives by the lake.