Ono-i-Lau is a group of islands within a barrier reef system (ono is six in the Fijian languages). There are three central volcanic islands, the uppermost parts of the volcanic edifice rising from the Lau Ridge slightly more than 1000 m below sea level and on which the reef and other islands are built. There are also three clusters of coral limestone islets, Yanuya (50 islets) and Mana (46 islets) on the barrier reef and Niuta (7 tiny islets). A sand cay, Udui, is not counted as one of the six “islands”.