Out of the approximately 100 islands, only 16 are inhabited. The main island of the group is known as Mainland and of the next largest, Yell, Unst, Fetlar lie to the north and Bressay and Whalsay to east. East and West Burra, Muckle Roe, Papa Stour, Trondra and Vaila are smaller islands to the west of Mainland. The other inhabited islands are Foula 28 kilometres (17 mi) west of Walls, Fair Isle 38 kilometres (24 mi) south-west of Sumburgh Head, and the Out Skerries to the east. The uninhabited islands include Mousa, known for the Broch of Mousa, the finest preserved example in Scotland of these Iron Age round towers, St Ninian's Isle connected to Mainland by the largest active tombolo in the UK, and Out Stack, the northernmost point of the British Isles. Shetland's location means that it provides a number of such records: Muness is the most northerly castle in the United Kingdom and Skaw the most northerly settlement.
