What is "athelney"

Athelney is located between the villages of Burrowbridge and East Lyng in the Sedgemoor district of Somerset, England. The area is known as the Isle of Athelney, because it was once a very low isolated island in the 'very great swampy and impassable marshes' of the Somerset Levels. Much of the Levels are below the level of high tide. They are now drained for agricultural use during the summer, but are regularly flooded in the winter.

Athelney is around 6 miles from North Petherton, where the Alfred Jewel (an Anglo-Saxon ornament dating from the late 9th century) was discovered in 1693.