St Ninian's Isle is a small
tied island connected by the largest active
tombolo in the UK to the south-western coast of the
Mainland, Shetland, in
Scotland. The tombolo, known locally as an
ayre from the
Old Norse for "gravel bank", is 500 metres long. During the summer the tombolo is above sea level and accessible to walkers. During winter, stronger wave action removes sand from the beach so that it is usually covered at high tide, and occasionally throughout the tidal cycle, until the sand is returned the following spring. Depending on the definition used, St. Ninian's is thus either an
island, or a
peninsula; it has an area of about 72
hectares. The nearest settlement is
Bigton on South Mainland. The important
early medieval St Ninian's Isle Treasure of metalwork, mostly in silver, was discovered under the church floor in 1958. Many seabirds, including
puffins, visit the island, with several species nesting there.