Blessington Lakes is officially known as Poulaphouca Reservoir, and it's only one lake. Construction of the dam began in 1937 and by the time it was completed, and the valley flooded, it became the largest man-made lake in Ireland. It supplies water to Dublin and the water is used to power a hydroelectric power plant.
The lakeside trails are popular with walkers and cyclists and the lake is home to many water birds, including breeding pairs of the rare goosander.