The ring wall and the ruins — Visby's two great sights define its skyline — the ring wall, a near-complete medieval town wall over three kilometres long, studded with dozens of towers, that you can walk beside and along in stretches; and the church ruins, the roofless Gothic shells of a dozen or more medieval churches that failed when the town's fortunes did, now standing dramatically among the lanes. Between them rises St Mary's Cathedral, the one that survived intact. Walking the wall and the ruins, tracing the medieval town, is the essential Visby experience.
Roses, ruins and cobbled lanes — Visby's nickname, the "town of roses and ruins," captures it — a maze of steep cobbled lanes and small squares, lined with merchant houses and little wooden cottages draped, in summer, with climbing roses, sloping down toward the sea. There's no single sight so much as the whole atmospheric town to wander; get lost in the lanes, find the ruins and the flower-hung doorways, and take a fika (coffee and cake) in a courtyard café. It's at its most magical in the long summer light of the Baltic evenings.
Gotland: beaches, rauks and Fårö — Visby is the gateway to Gotland, and the island rewards exploring — long beaches and coves for swimming in summer, the striking limestone sea stacks (rauks) that rise from the shore, medieval countryside churches, and, to the north, the wild, spare island of Fårö, with its rauk fields and its associations with the filmmaker Ingmar Bergman, who lived and is buried there. Hire a bike or a car and get out of town for a day of the island's nature and quiet. It's a different, elemental side of the visit.
Summer, festivals and Swedish flavours — Visby comes alive in the Baltic summer, when Swedes flock over for the sun, the sea and the atmosphere, and the Medieval Week festival (August) fills the town with costumes, markets and tournaments. The food is Swedish with a Gotland accent — Gotland lamb, the saffron pancake (saffranspannkaka) with berries and cream, fresh Baltic fish, and local truffle and asparagus in season, with a growing scene of island producers. Eat in the old-town restaurants and the harbour, and lean into the long, light summer evenings.