Kiribati - Topography

With the exception of Banaba, an upthrust coral formation that reaches a high point of 265 m (868 ft), the islands are coral atolls built on a submerged volcanic chain and seldom rise more than 4 m (13 ft) above sea level. Christmas Island is the largest atoll in the world, with an area of 606 sq km (234 sq mi). In most of the atolls the reef encloses a lagoon, on the eastern side of which is a narrow stretch of land varying in length from about 45 m (150 ft) to 80 km (50 mi).