Mavis Grind is where Northmavine begins (the giant stainless steel sign is a clue!) moving north along the main A970 from the district of Delting. At this point ('grind' means gate and 'Mavis' means 'of the narrow isthmus') there's just 100 metres or so between the Atlantic Ocean (St Magnus Bay) to the west and the North Sea (Ell Wick and Sullom Voe) to the east. Until the early 1950s, some of Shetland's east coast fishermen would regularly haul their boats across the Mavis Grind isthmus to reach the rich fishing grounds of the west.
It was always thought that the vikings would use Mavis Grind to move their longships from west to east or vice versa in order to avoid the dangerous northern and southern tips of the Shetland Mainland. in 1999 the adventurer Robin Knox-Johnston enlisted hundreds of Shetlanders in an attempt to recreate this with a replica viking galley. Eventually, with the help of a tractor, he succeeded, but the boat was damaged and afterwards the feeling was that full-size Norse galleys would probably have taken the sea route.
If you park at Mavis Grind and explore the west coast, you will find first the amazing geology wall, giving you an insight into Northmavine's extraordinary rock formations, and, after a splendidly energetic climb and walk, a chambered cairn, Neolithic house, an old otter hoose or trap - unused now. If you're very lucky, you may find "The Hol of Hellier" at Turvalds Head. This has a tiny entrance but space inside for up to a dozen folk to hide from the press gang, back in the days when Shetland sailors were much sought after by the Royal Navy. If you do find it, don't get stuck.
By the way, there's some great sea angling to be had, casting from the armouring on the east side of Mavis Grind, and this can be a place to see visiting whales. The 'otters crossing' sign is famous, and very necessary.