Place in California where Stan Lee's Superhumans took place (s1, ep3 12hr marathon) ?

[iTaliaBoi24]

Where was the 12-hour challenge run? all i could pick out (missed the first 10 minutes) was that it was 30.4 miles back to San Francisco. I'm assuming it was near Napa or somewhere? I REALLY want to bike and explore the roads around there and wanted to know where this is!!?!

thanks much!