We will only be spending 3.5 days in London - our first trip there - and would like to spend one of those days on a day trip outside of London. Stonehenge is a definite, simply because I've always been fascinated by it and don't want to leave England without having seen it. I've checked out every possible tour, and my question is...if you could only choose one, would you recommend visiting Windsor Castle, Salisbury or Bath? Why? Thanks for your advice.