Marktgasse is the main street of Feldkirch's old town, lined with arcades, painted facades, shops, and cafes. It is compact but handsome, and it gives the town its strongest first impression.
The best way to see it is slowly: look through the side lanes, step under the arcades when it rains, and keep an eye out for the old gates that still mark the medieval street plan. Feldkirch is small enough that wandering is more useful than a checklist.