Treasure Hunt - ideas?

I am thinking of running a "treasure hunt" in a French town for some English friends, for fun and to help with their French language. This will be a list of say 20 questions they have to find the answers to. Eg on what river does Valence stand? where they probably have to ask someone, and "translate the Plat du Jour at the Entreacte restaurant. Any ideas, I'd like to get them talking to people not just looking at dates, road names etc.