it’s a great ride! It’s not extremely difficult but definitely a good workout when you only have about an hour to kill. It’s pretty much uphill the way there with a few rolling hills. Nice views of the hillside along the way up and once you get to the top (which is where the loop starts) it’s a bit more flat but a very nice scenery. I think it’s technically into Napa at that point. Once you loop around it’s a great descent and not too windy of roads so you can really go fast. At the bottom, the last two turns are probably the most dangerous because it’s steep and sharp. The last turn is where I crashed actually. Once you make that you’re done!
As a bonus, you can head left onto Thornsberry, which is paved poorly but has a few moderate rolling hills taking you through some nice mountain side houses. That leads to the back entrance to Gundlach Bundschu Winery, which you can ride through and make your way back to the highway to lead either to Napa or back to Sonoma.