Isolated from the Llŷn Peninsula on the mainland by two miles of treacherous sea, Bardsey is two miles long has a coastline of five miles, rises to 548 feet and is located three miles south west of Braich y Pwll.

Its original name is Norse, but its Welsh name, Ynys Enlli, is much more descriptive and it means either 'island of the great current' or 'the island in the tides'.

At times, the wind and the fierce sea currents make sailing between the island and the mainland very dangerous. Sometimes it can be impossible to reach or leave Bardsey for weeks. In the autumn of 2000 17 island visitors became stranded for two weeks when gales prevented a boat from Abersoch going to rescue them.

Bardsey was inhabited in Neolithic times, and there are still traces of hut circles. During the fifth century the island became a refuge for persecuted Christians and the monks built their first abbey in the sixth century. The pilgrims' way to Bardsey was once as famous as that of Lindisfarne and Iona, and three pilgrimages to Bardsey were equal to a pilgrimage to Rome.

Throughout the Dark Ages many pilgrims remained on the island, they died and were buried on Bardsey and it became known as 'the Isle of Twenty Thousand Saints'.

For centuries Bardsey was important as 'the holy place of burial for all the bravest and best in the land'. Welsh bards called it 'the land of indulgences, absolution and pardon, the road to Heaven, and the gate to Paradise'.

There has been a church on Bardsey for over 1,700 years, but the only part remaining of the Augustinian Abbey, which was built in the 13th century, is the tower.

It has recently been discovered that a gnarled and twisted apple tree is the only survivor of an orchard that was tended by the monks who lived on Bardsey 1,000 years ago. The ancient tree is only a short distance from a cave where the legendary King Arthur and Merlin are believed to have been buried. A 12th century historian claimed that Avalon was an island of apples, and its name was deduced from the Welsh word, afal. Experts on the varieties of British apples believe that this strain of apple is the only one in the world, and cuttings from the tree have been planted so that they can be sold to raise money for the Bardsey Trust.

According to legend, the Thirteen Rarities of King Arthur's regalia were brought to the House of Glass on Bardsey which was identified as Avalon. This was the island where Arthur's wounds were healed and the last resting place of King Arthur, and Merlin, the wizard or magician, who was prominent in the legends of King Arthur and the Round Table.

Like many islands during the 17th century, Bardsey was a pirates' lair, the pirates being the local gentry who were involved in illegal activities. By the end of the 19th century there were 111 farmers and fishermen with their families living on the island, and their landlord was Lord Newborough. He appointed a "king" to settle any disputes, and the office continued until a few years after the end of the 1914-1918 Great War.

The red banded lighthouse at the tip of Bardsey Island is the tallest in the British Isles with a square tower. As it stands on the route of migrating birds, the powerful flashing light dazzled them and many birds have flown into the lantern and been killed.