Whiskeytown Lake is the site of a former mining town that was dammed in 1963. It's a popular recreation area with four neighboring waterfalls that are fairly accessible. The annual Waterfall Challenge takes place in April—hike to all four waterfalls within the designated week either on your own or alongside a scheduled ranger-led excursion. That's a scenic challenge.
Whiskeytown's National Recreational Area site is here.