There is no such thing as a simple walk in Assisi. Nor should one ever consider a brisk walk. There is something special about every single inch of the town. Ancient streets, built atop streets that are even older. Homes built side by side, stone facades, pan tile roofs and beautiful doorways. Flower pots, vines creeping gracefully up alongside a doorway, all the most common of uncommon sights. Everything up a hill or a steep incline. A StairMaster salesperson would go completely broke here. The only ones who seem to find it to be a problem are the unsuspecting tourists who huff, puff and complain as they pass in little groups. Every time I have observed the ritualistic huffing and puffing, it has come from folks who appear to be with a tour group. "A Day in Assisi" is what they were sold. They come to see the "cute" little town, the "churches" and have a limited amount of time to spend. They've also probably spent a day in Rome and one in Florence.
Oh, I'm sure that the tour guides provide a lot of useful and interesting information. I know the level of difficulty involved in becoming a licensed tour guide in Italy. It isn't easy. But, I've learned that the best guide oftentimes is one's heart.