Søby sits at the northern tip of Ærø, 15 km from Ærøskøbing and 23 km from Marstal. It is the third of the island's towns and the smallest — a working fishing harbour with a small shipyard that still builds and repairs steel vessels. The atmosphere is unfussed: nets drying on the quay, a couple of seasonal cafes, and a ferry running across to Fynshav on the island of Als in southern Jutland.
For travellers the interest is mostly the harbour itself, the short walk out to the lighthouse at Skjoldnæs at the very tip of the island, and the views back across the water to Funen. The Skjoldnæs lighthouse, built in 1881, is a slender white tower at the end of a flat headland of grazing land and golf course — a good destination for a quiet afternoon's cycle from Ærøskøbing.