I joined 2 friends in St. Helena to ride up Spring Mountain to Santa Rosa, and then back through Calistoga. The climb was quite brutal (I had to stop a few times for my heart rate to drop down from a very uncomfortable 175bpm!) but it was worth it!
Instead of heading down Petrified Forest Rd to Calistoga, we took a part-dirt road called Sharp road, which was a bit scary, but the views were epic. The scenic pictures here are taken from Sharp Road.