I'm going to have a day in Maastricht this fall and I'm looking for a walking tour that hits the major sights. For convenience and timing sake, a tour that's either online, in an app, from a good blogger, etc. - basically something that I can do completely on my own. Yes, there are city sponsored tours or tours that can be bought, but I'd like something akin to the tours that Rick has in his books. Any great ones out there?