Depends how you define "favourite". In terms of sites that I find evocative, beautiful, enigmatic, moving.... no, Stonehenge doesn't even get a look-in. As a unique site of incredible importance, it's probably top of the list. But on a personal level, I'm just not that interested. I can't divorce the experience from the roads, the crowds, the fence, the commercialisation. Lift it up and dump it on Dartmoor and I'll review my opinion!