Whiskeytown National Recreation Area
Whiskeytown is a outdoor recreational haven for tourists and locals alike, a land of water, hills, and mountains transformed (for better or worse) by the activities of man. It also has a legacy of historic preservation. That said, is anything you do may disturb others enjoying what the area has to offer, don't do it. Use common sense.
Gold, quartz, and copper were all mined in different parts of the area at different times in Whiskeytown's history. After the Central Valley Project altered the hydrology of the Sacramento River watershed, the lake was formed, flooding the actual town of Whiskeytown. Its ruins are now located at the bottom of the lake, much like Kennett under nearby Shasta Lake.
The area is mostly covered by forested hills and mountains, and, of course, Whiskeytown Lake itself. There are also a few gulches juttung on the other side of CA-299 from the lake proper.
Flora and fauna
Fish are abundant in the lake. Small animals (squirrels are very common) abound, as do larger ones such as bears and mountain lions.
Definitely cooler than Redding! Temperature is variable near the shore and on the lower slopes, and usually colder as you go upslope from there. Rain is common any month but summer. Snow comes in winter and spring in all areas of the park. Hail, when it falls, usually occurs at higher elevations in late fall and early spring.
Get in or out
CA-299 is the way to go. Bikes are not recommended. If you don't have a car, carpool. Do not hitch-hike or pick up hitch-hikers. Unfortunately, it is not safe in this part of the country.
There is a $5.00 day pass, a $10.00 week pass, and a $25.00 annual pass. The latter is also valid at Lassen Volcanic National Park, the annual pass for which is interchangeable with the one for Whiskeytown.
More information: 
By car, or by using the trails is best.
Bears and mountain lions roam the area, so watch out! Staying on trails is a good idea.