Torggatan is Mariehamn's main commercial street, running north-south through the centre of town. It is lined with wooden buildings, small shops, a handful of restaurants and cafés, and trees that create a pleasant shaded promenade in summer. The street is wide enough to be comfortable and quiet enough to walk without traffic stress.
Most of what you need in Mariehamn is on or immediately off Torggatan: the tourist office, the post office, the main supermarkets, and the bulk of the town's cafés. It is the kind of main street that serves a small community well without pretending to be something it isn't. The Sunday farmer's market (seasonal) takes place in the square at the north end.