It consists of approximately 1,190 coral islands grouped in a double chain of 26 atolls, spread over roughly 90,000 square kilometers, making this one of the most disparate countries in the world. Composed of live coral reefs and sand bars, the atolls are situated atop a submarine ridge 960 kilometers long that rises abruptly from the depths of the Indian Ocean and runs from north to south. Only near the southern end of this natural coral barricade do two open passages permit safe ship navigation from one side of the Indian Ocean to the other through the territorial waters of Maldives. For administrative purposes the Maldives government organized these atolls into nineteen administrative divisions.
The largest island of Maldives is Gan, which belongs to Laamu Atoll or Hahdhummathi Maldives. In Addu Atoll the westernmost islands are connected by roads over the reef and the total length of the road is 14 km.
Most Atolls of the Maldives consist of a large, ring-shaped coral reef supporting numerous small islands. Islands average only one to two square kilometers in area, and lie between one and 1.5 meters above mean sea level. Although some of the larger atolls are approximately 50 kilometers long from north to south, and 30 kilometers wide from east to west, no individual island is longer than eight kilometers. Maldives has no hills, but some islands have dunes which can reach 2.4 meters / 8 feet above sea level, like the NW coast of Hithadhoo (Seenu Atoll) in Addu Atoll. Islands are too small to have rivers, but small lakes and marshes can be found in some islands.
On average, each atoll has approximately 5 to 10 inhabited islands; the uninhabited islands of each atoll number approximately 20 to 60. Some atolls, however, consist of one large, isolated island surrounded by a steep coral beach. The most notable example of this type of atoll is the large island of Fuvahmulah situated in the Equatorial Channel.
The tropical vegetation of Maldives differs in the inhabited and in the uninhabited islands. Inhabited islands have small groves of banana, papaya, drumstick and citrus trees by the homesteads, while breadfruit trees and coconut palms are grown in available patches of land. On the other hand uninhabited islands have mostly different kinds of bushes (magū, kuredi, kandū, boshi) along the waterline as well as some coconut trees.
Some islands are marshy, while others are higher owing to sand and gravel having been piled up by wave action. Often the soil is highly alkaline, and a deficiency in nitrogen, potash, and iron severely limits agricultural potential. Ten percent of the land, or about 26 km², is cultivated with taro, bananas, coconuts, and other fruit. Only the lush island of Fuvammulah produces fruits such as oranges and pineapples partly because the terrain of Fuvammulah is higher than most other islands, leaving the groundwater less subject to seawater penetration. However, as population grows, even in this island the cultivated areas are shrinking rapidly.
Freshwater floats in a layer known as "Ghyben/Hertzberg lens" above the seawater that permeates the limestone and coral sands of the islands. These lenses are shrinking rapidly on Male and on many islands where there are resorts catering to foreign tourists. Mango trees already have been reported dying on Male because of salt penetration. Most residents of the atolls depend on groundwater or rainwater for drinking purposes.