The name is older than anyone's records. High German speakers heard Heiligland - holy land - and Frisians heard their own Halunder, which one school of linguists insists meant simply high land, the high place sticking out of the flat sea. The locals, who still speak Heligolandic, a North Frisian dialect, lean toward the second reading. Either way, the place felt sacred long before it was strategic. Norse worshippers placed the god Forseti's central sanctuary here. The Austrian writer Jürgen Spanuth thought it might be Atlantis. Sixty-one metres above the surrounding sea, the Oberland - the upper plateau - has yielded prehistoric burial mounds and copper plates that suggest the island was a workshop and a holy site long before any Hanseatic merchant heard of it. Until 1720, what is now two islands was one. A storm flood that year split the rock from the sandy Düne next door, and the channel has been there ever since.

Heligoland's nineteenth century was unexpectedly literary. After 1826 the British turned the island into a seaside spa, and the European upper class came in droves for the brilliant North Sea light, the cliff walks, and what The Leisure Hour called "a land where there are no bankers, no lawyers, and no crime." The visitors included Heinrich Heine and August Heinrich Hoffmann von Fallersleben. In 1841, Hoffmann sat down on Heligoland and wrote the words to the Deutschlandlied - the song that would become, two stanzas later, the national anthem of Germany. Eighty-four years afterward, a young physicist named Werner Heisenberg, hay-fevered and frustrated, fled Göttingen for the pollen-free cliffs. In the summer of 1925, walking the Oberland and watching the sea, he sketched out the equations of matrix mechanics. Quantum theory has a birthplace, and it is this island. Carlo Rovelli titled his 2020 book about it simply Helgoland.

Germany fortified Heligoland as soon as it took possession. By the First World War the cliffs bristled with 364 guns, 142 of them on disappearing carriages, all behind ten rows of naval mines. The first naval action of that war - the Battle of Heligoland Bight in August 1914 - was fought within sight of the island. Between the wars Hitler's engineers launched Project Hummerschere, "Project Lobster Claw," to expand the fortifications until Heligoland would rival Britain's Scapa Flow. The project was never finished. In April 1945, two waves of bombing dropped about 7,000 bombs on the island in two days. The civilians, sheltering in tunnels under the cliffs, mostly survived. The German garrison did not. Just before that raid, an islander resistance group led by Georg Braun and Erich Friedrichs had tried to surrender Heligoland to the Allies without a fight. They were betrayed, arrested, and five were executed by firing squad at Cuxhaven on 21 April 1945. Six Stolpersteine - stumbling stones - now mark their names on the island's roads.

On 18 April 1947, exactly two years after the bombing raids, the Royal Navy detonated 6,700 tonnes of leftover munitions in the tunnels and submarine bunker beneath the southern half of the island. The British called it Operation Big Bang. It was the largest non-nuclear explosion ever planned to that date - thirteen terajoules, about 3.2 kilotons of TNT equivalent. The blast was meant to wipe Heligoland off the map. It didn't. The porous red sandstone vented the shockwave upward, the cliffs cracked and slumped, the southern tip blew off, and the rubble landed in a heap that islanders now call the Mittelland, the Middle Land. But the island itself, against every British calculation, remained. The flak tower at the centre survived and was converted, in 1952, into a lighthouse - the same lighthouse that still throws the strongest beam on the German coast. That same year, after years of campaigning by exiled islanders, Britain returned Heligoland to West Germany.

Modern Heligoland is car-free by law - the Straßenverkehrsordnung, section 50, bans both automobiles and bicycles, with a few exceptions for emergency services and the single police vehicle the island took delivery of in 2006. Day-trippers can triple the population in summer. The duty-free status, a legacy of the island's peculiar customs history, keeps the harbour shops busy. The Lange Anna, a forty-seven-metre sandstone sea stack off the northwest corner, stands as the island's signature silhouette. Bird ringers still come for the migrations Heinrich Gätke first catalogued in the 1890s, when his book on Heligoland's birds became the founding text of European migration studies. The Biological Station of Helgoland, founded in 1892, is still here too. Cliffs, gulls, a lighthouse made from a flak tower, and a Frisian dialect spoken by a few hundred people - the island has outlasted everyone who came to claim it.