Not quite a solo vacation, but I used to join my wife on her business trips when she worked for an airline. I would only see her after dinner, so I was on my own for the rest of the day. It was a great way for me to have a golf vacation.
I travelled to Scotland, London, and Paris for 10 days alone. Only issue was the panhandlers in Paris. Once you learn how to avoid them, you're fine. (They will try anything to scam you, shrug, walk away...)
