Feeling quite adventurous, a few weeks ago we decided to test our legs on Mix Canyon Road a bicycle ride located just on the western side of Vacaville. We've heard amazing things from our biking friends about this road ("23% Grade! -- Steeper than the Steepest Part of the Tour De France!") and wanting to work off a little of our post-holiday gluttony thought it would be good for us.
So... We were kind of right. After fighting up the 2400 Vertical Feet in about five miles, we felt as if our hearts were about to explode, especially between miles 4.3 and 4.4, where it hits its steepest patch (the aforementioned 23% grade). For a lot of the road, it was so steep that we had cut back and forth against the grain of the road to stop ourselves from falling over -- completely unable to power straight up the hill. In the end, however, it was completely worth it. The views from the top were stunning. Sitting down and eating a Cliff Bar after the climb we marveled at the view of the bay and in the far background were able to make out the twin towers of the Golden Gate Bridge. Of course, our stupid camera wasn't able to pick out that level of detail and we were only to capture some okay pictures.
For those not bicycling included, it is possible to drive to the top just to see the views. On a clear day it is quite spectacular, the ascent has views to the East, looking down the central valley while cresting the ridge to the top gives some of the best views of the Northern Bay Area that we have ever seen. All in all, highly recommended.