Llyn Brianne is a Spectacular man-made lake and reservoir in the headwaters of the River Tywi in Mid Wales. The reservoir was constructed by Wimpey Construction in the late 1960s and early 1970s. The dam is made up of crushed rock, It holds over 64 million cubic metres of water contained by a 91m (300ft) stone-built dam and is the largest of its kind in Europe. Llyn Brianne did not exist until the early 1970’s. The dam is the UK's TALLEST, standing dam at a height of 300 ft (91 m). In 1996 the reservoir spillway was increased by 1 metre in height and a hydro electric generating station was added at the base of the dam. When all three turbines are working, it generates 4.60 megawatts of electricity. The spillway of the dam is a notable tourist attraction when the reservoir is spilling.