That canal still marks the island's central seam. North of it, the ground is sand and gravel dropped by retreating ice; south of it lie boulder clay and outwash plains, which is why the north feels wilder — wavy meadows, patches of woodland, scraps of heath. The coastline runs to steep cliffs and stony beaches, with sandy stretches wedged between them where swimming is possible. Ballebjerg, northwest of Nordby, is the island's high point at just 64 metres. At the northern tip, Issehoved trails off into the sea in a way that has been described as a miniature of Skagen's Grenen. On the east side, the shallow lagoon of Stavns Fjord is held back from the Kattegat by Besser Rev, a sandbar seven kilometres long that can be walked to its tip at low tide — except during the breeding season, when the birds have priority. Hjortholm is the largest island inside the lagoon. Tranebjerg, the biggest town, sits on the South Island among eighteen villages and hamlets.

People have hunted here since the ice let go. Samsø became an island roughly 9,000 years ago, and the landscape is stitched with dolmens, passage graves, burial mounds and kitchen middens; excavations at Tønnesminde and Endebjerg turned up habitation running from the Stone Age through to the Viking Age. The sagas took the place seriously. Saxo Grammaticus set a legendary battle here, in which the Swedish champion Hjalmar and his friend Orvar-Odd fought the twelve sons of the berserker Arngrim — a fight famous enough to surface in Faroese ballads, in Orvar-Odd's saga and in the Hervarar saga. Afterwards the dead berserkers' mounds were said to be haunted, which did not deter Arngrim's granddaughter Hervor from walking up to them and demanding the enchanted sword Tyrfing from her father Angantyr. Samsey, as the Norse called it, is also where Odin, under the name Jalk, is said to have learned the magic of seid.

Through the Middle Ages the island belonged to the Crown, and the Crown fortified it heavily: Vesborg, where the lighthouse now stands; Gammel Brattingsborg, under the present town of Tranebjerg; Hjortholm on its islet in Stavns Fjord; Bisgård at the bishop's residence in Onsbjerg parish; and little Blafferholm in the garden of Brattingsborg manor. Not one survives above ground. The National Museum of Denmark finished archaeological fieldwork on the sites in 2012. Later centuries left quieter scars. From 1831 to 1857 the tiny island of Kyholm, just east of Samsø, served as a quarantine station for ships arriving with plague or cholera aboard; an abandoned cemetery of about a hundred graves is still there. In 1940 the Wehrmacht made Samsø an outpost. When an American B-17 crash-landed at Alstrup, islanders hid several of the crew, including co-pilot Miles McCormack, until the Germans found them. Every man aboard survived the war except tail gunner Douglas Farris, killed in the air.

In 1997 Samsø won a Danish government competition to become a model renewable energy community. At the time it burned oil and coal, all of it shipped in from the mainland. Eleven onshore wind turbines went up, the first feeding the grid in 2000, and ten offshore turbines followed in 2003 — twenty-one machines and 30 MW in total, funded by the islanders themselves rather than by a utility. That detail is the whole story. Farmers built straw-fired district heating into a network that now runs to four plants, and some grow the biofuel their vehicles burn. The island generates an annual equivalent of 100% of its electricity from wind, exporting the surplus across the water, and draws about 75% of its heat from local solar and biomass. An Energy Academy in Ballen serves as the meeting hall for all of it. The current target is to be free of fossil fuels by 2030 — twenty years ahead of the national deadline.

Farming has shaped Samsø for millennia, and nearly the whole island is cultivated landscape. Close to 16% of islanders work in farming or fishing, against 3.5% nationally. Free-range production dominates, mostly potatoes, vegetables and berries, and through the 2000s more of the packing and processing moved onto the island itself, keeping the money local. Samsø's early new potatoes are a national event: the first few pounds of the season routinely fetch around £100. Just north of Nordby sits a stranger crop — Labyrinten, laid out in 2000 across 60,000 square metres of conifer woodland grown on a former Christmas tree plantation, and reckoned the world's largest permanent labyrinth. Roughly 3,600 people live here year-round, on an island that keeps finding new uses for the same ground.