Map showing all locations mentioned on Wikipedia article:
Mavis Grind is a narrow
isthmus joining the Northmavine peninsula to the rest of Shetland
Mainland in the
Shetland
Islands, UK. It
is just 33 metres wide at its narrowest point. The name means 'gate
of the narrow isthmus' in the local dialect.
It carries
the main A970 road to Hillswick in the
north west of Shetland and is a few miles from the settlement of
Brae.
Mavis
Grind is said to be the only place in the UK where you can toss a
stone across land from the North Sea to the Atlantic Ocean. It is a regular crossing point for otters, which in Shetland are
sea-dwelling.
Remains of a late Bronze Settlement have been found close by.