Atoll remains of an ancient atoll as a hill in a limestone area is called a reef knoll. The second largest atoll by dry land area is Aldabra with 155 km². The largest atoll in terms of island numbers is Huvadhu Atoll in the south of the Maldives with 255 islands. In 1842, Charles Darwin explained the creation of coral atolls in the southern Pacific Ocean based upon observations made during a five-year voyage aboard from 1831 to 1836. Accepted as basically correct, his explanation involved considering that several tropical island types—from high volcanic island, through barrier reef island, to atoll—represented
Shaviyani Atoll of Milandhoo. This decision was vetoed by President Nasheed, and Milandhoo continued as the seat of the atoll office. The issue surfaced once again on February 26, 2011 when home rule was introduced into the country and the atoll offices were to be rebranded as the secretariats for the newly formed atoll councils. According to the Decentralization Bill, under which the councils were formed, the respective secretariats were to be seated in the capital islands of each atoll as stipulated in the new constitution of 2008, which in Shaviyani Atoll's case is Funadhoo. In the first atoll council meeting, it