Lyonesse

Lyonesse (/liːɒˈnɛs/ lee-uh-NESS) is a legendary kingdom said to have once stretched from Land’s End, at the southwestern tip of Cornwall, England, to the present-day Isles of Scilly in the Celtic Sea. According to myth, this land was lost in a single night, swallowed by the ocean. The people of Lyonesse were believed to live in prosperous towns, cultivating rich lowlands and worshipping in over 140 churches. Its most remarkable landmark was a grand, castle-like cathedral, thought to have stood atop what is now the Seven Stones Reef—located roughly 18 miles (29 km) west of Land’s End and 8 miles (13 km) northeast of the Isles of Scilly. The name is sometimes spelled "Lionesse."

Lyonesse also features prominently in Arthurian legend, particularly in the tale of Tristan and Iseult. It was the homeland of the knight Tristan, whose father, King Meliodas, ruled the kingdom. After Meliodas’s death, Tristan was the rightful heir, but he never claimed his inheritance—the land vanished beneath the sea while he was away at the court of his uncle, King Mark of Cornwall.

Later versions of the legend describe the kingdom’s destruction as a cataclysmic event, with some claiming it happened overnight on either November 11, 1099, or a decade earlier. One version of the story attributes the sinking to divine punishment: the people of Lyonesse had committed a terrible, unspecified sin, provoking God’s wrath. A violent storm struck during the night, unleashing a massive wave that engulfed the entire kingdom.