Kielder Reservoir is located in Northumberland, England, and is the largest man-made lake in the country. It was created in the 1970s to supply water to the growing population in the northeast and to help control flooding in the area. The reservoir is surrounded by the scenic Kielder Water & Forest Park, which offers various outdoor activities such as hiking, cycling, and birdwatching. The reservoir covers an area of approximately 1,200 acres and has a capacity of around 200 billion liters of water. It is also home to a variety of wildlife, including otters and red squirrels, making it an important ecological site. Visitors can enjoy stunning views and participate in water sports like sailing and kayaking.