There is a legend of the lost lands off the coast of Cornwall, between Land's End and the Scillies. The Land of Lyonesse
Many areas have such tales of land disappearing beneath the sea. Lyonesse has been variously identified with Lothian in Scotland, Leonais in Brittany, Cantref Gwaelod which once lay where Cardigan Bay now stretches, as well as in Cornwall where it was called Lethowstow.
In Cornwall the sixteenth-century antiquarian, William Camden, collected a
number of folk tales from the local people in which they refer to the Seven
Stones reef off Land's End as the City of Lions (Lyonesse). They also claimed
that one could hear the bells of the drowned city of Lyonesse ringing out during
rough seas. Today the remains of field boundaries show up at low tide along
the sands of the Sampson Flats between the isles of Tresco and Sampson in the
Scilly Isles.
According to legend Lyonesse was ruled by Tristan's father. On his death, Tristan
became ruler of Lyonesse, but never took his throne as he was at his Uncle
Mark's court in Cornwall.
And it was apparently at this time that Lyonesse sank beneath the sea. Today
various local folklore has stories of Lyonesse.