Asia's smallest and least-known nation; the Republic of Maldives; lies scattered from north to south across a 750-kilometre sweep of the Indian Ocean 500 kilometres south-west of Sri Lanka. More than 1000 islands; together with innumerable banks and reefs; are grouped in a chain of nineteen atolls which extends from a point due west of Colombo to just south of the equator.

The atolls; formed of great rings of coral based on the submarine Laccadive-Chagos ridge; vary greatly in size. Some are only a few kilometres square; but in the far south the great atoll of Suvadiva is sixty-five kilometres across; and has a central lagoon of more than 2000 square kilometres. The northern and central atolls are separated from each other by comparatively narrow channels of deep water; but in the south Suvadiva is cut off by the eighty-kilometre-wide One-and-a-half-Degree Channel. Addu Atoll is still more isolated; being separated from the atoll of Suvadiva by the seventy-kilometre-wide Equatorial Channel.