 Orkney is situated 16 kilometres ( 10 mi ) north of the coast of mainland Scotland , from which it is separated by the waters of the Pentland Firth . The largest island , known as the " Mainland " has an area of 523 @.@ 25 square kilometres ( 202 @.@ 03 sq mi ) , making it the sixth largest Scottish island . The total population in 2001 was 19 @,@ 245 and the largest town is Kirkwall . Shetland is around 170 kilometres ( 110 mi ) north of mainland Scotland , covers an area of 1 @,@ 468 square kilometres ( 567 sq mi ) and has a coastline 2 @,@ 702 kilometres ( 1 @,@ 679 mi ) long . Lerwick , the capital and largest settlement , has a population of around 7 @,@ 500 and about half of the archipelago 's total population of 22 @,@ 000 people live within 16 kilometres ( 10 mi ) of the town . Orkney has 20 inhabited islands and Shetland a total of 16 . 
