Llwyn-on Reservoir is the largest and southernmost of the three reservoir

Reservoir

A reservoir , artificial lake or dam is used to store water.Reservoirs may be created in river valleys by the construction of a dam or may be built by excavation in the ground or by conventional construction techniques such as brickwork or cast concrete.The term reservoir may also be used to...

s in the Taff Fawr valley in South Wales

South Wales

South Wales is an area of Wales bordered by England and the Bristol Channel to the east and south, and Mid Wales and West Wales to the north and west. The most densely populated region in the south-west of the United Kingdom, it is home to around 2.1 million people and includes the capital city of...

. It is owned by Welsh Water

Welsh Water

Dŵr Cymru Welsh Water is a company which supplies drinking water and wastewater services to most of Wales and parts of western England.It is regulated under the Water Industry Act 1991.-History:...

. It is located in the Brecon Beacons National Park. The eastern half is in the Merthyr Tydfil

Merthyr Tydfil

Merthyr Tydfil is a town in Wales, with a population of about 30,000. Although once the largest town in Wales, it is now ranked as the 15th largest urban area in Wales. It also gives its name to a county borough, which has a population of around 55,000. It is located in the historic county of...

 unitary authority area and the western half is in the Rhondda Cynon Taff

Rhondda Cynon Taff

Rhondda Cynon Taf, or RCT, is a county borough in the South Wales Valleys of Wales. It consists of 3 valleys: the Rhondda Valley, Cynon Valley and Taff-Ely Valley...

 unitary authority area. The reservoir is within the historic county boundaries of Breconshire. The dam

Dam

A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 is adjacent to Llwyn-On village

Village

A village is a clustered human settlement or community, larger than a hamlet with the population ranging from a few hundred to a few thousand , Though often located in rural areas, the term urban village is also applied to certain urban neighbourhoods, such as the West Village in Manhattan, New...

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Nant Gwinau, Nant Car and Garwnant are the major streams that enter the reservoir.

There are a variety of guided walks and waymarked paths. Environmental sculpture

Environmental sculpture

The term environmental sculpture is variously defined. A development of the art of the 20th century, environmental sculpture usually creates or alters the environment for the viewer, as opposed to presenting itself figurally or monumentally before the viewer...

s can be found on the Wern and Willow walks. The Taff Trail

Taff Trail

The Taff Trail is a popular walking and cycle path that runs for between Cardiff Bay and Brecon in Wales. It is named so because it follows the course of the River Taff...

 and the Navvies Line paths link Cefn Coed-y-Cymmer to Brecon

Brecon

Brecon is a long-established market town and community in southern Powys, Mid Wales, with a population of 7,901. It was the county town of the historic county of Brecknockshire; although its role as such was eclipsed with the formation of Powys, it remains an important local centre...

. There is one bird hide

Bird hide

A bird hide is a shelter, often camouflaged, that is used to observe wildlife, especially birds, at close quarters. Although hides were once built chiefly as hunting aids, they are now commonly found in parks and wetlands for the use of bird watchers, ornithologists and other observers who do not...

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