Lake Kaweah, Sequoia National Park
This resevoir on the Kaweah River outside the park would probably fall under Lemon Cove or Three Rivers, but I'm putting it here. The lake is surrounded by the foothills of the Sierra, and there is one area where you can get a really good view of the lake backed by snow-capped Alta Peak. A lot of times, though, smog will really mess up the views. You can also boat on the lake, and there's (I believe) a visitor center near the dam.
Formed by the construction of the Terminus Dam on the Kaweah River, the lake provides many types of recreation activities for park visitors including boating, fishing, and camping.
Terminus Dam was completed in 1962 by the US Army Corps of Engineers to provide flood damage reduction and water conservation. During the spring run-off season it stores 185,000 acre feet of water. Energy production was added in 1990 with the construction of the Terminus Power Plant.