Cambodia covers 181,035 square kilometres in the southwestern part of the Indochina peninsula. It lies completely within the tropics; its southernmost points are only slightly more than 10° above the equator.
Roughly square in shape, the country is bounded on the north by Thailand and by Laos, on the east and southeast by Vietnam, and on the west by the Gulf of Thailand and by Thailand.
Much of the country's area consists of rolling plains. Dominant features are the large, almost centrally located, Tonle Sap (Great Lake) and the Mekong River, which traverses the country from north to south and is the 12th longest river in the world.
The climate is monsoonal and has marked wet and dry seasons of relatively equal length. Both temperature and humidity generally are high throughout the year.
Forest covers about two-thirds of the country, but it has been somewhat degraded in the more readily accessible areas by burning (a method called slash-and-burn agriculture), and by shifting agriculture.
Cambodia falls within several well-defined geographic regions. The largest part of the country, about 75 percent, consists of the Tonle Sap Basin and the Mekong Lowlands.
To the southeast of this great basin is the Mekong Delta, which extends through Vietnam to the South China Sea.
The basin and delta regions are rimmed with mountain ranges to the southwest by the Cardamom Mountains and the Elephant Range and to the north by the Dangrek Mountains. Higher land to the northeast and to the east merges into the Central Highlands of southern Vietnam.
The Tonle Sap Basin-Mekong Lowlands region consists chiefly of plains with elevations generally of less than 100 meters. As the elevation increases, the terrain becomes more rolling and dissected.
The Cardamom Mountains in the southwest, oriented generally in a northwest-southeast direction, rise to more than 1,500 meters. The highest mountain in Cambodia--Phnom Aural, at 1,771 meters—is in the eastern part of this range.
The Elephant Range, an extension running toward the south and the southeast from the Cardamom Mountains, rises to elevations of between 500 and 1,000 meters.
These two ranges are bordered on the west by a narrow coastal plain that contains Kampong Saom Bay, which faces the Gulf of Thailand.
This area was largely isolated until the opening of the port of Kampong Saom (formerly called Sihanoukville) and the construction of a road and railroad connecting Kampong Saom, Kampot, Takev, and Phnom Penh in the 1960s.
The Dangrek Mountains at the northern rim of the Tonle Sap Basin consist of a steep escarpment with an average elevation of about 500 meters, the highest points of which reach more than 700 meters.
The escarpment faces southward and is the southern edge of the Korat Plateau in Thailand. The watershed along the escarpment marks the boundary between Thailand and Cambodia.
The main road through a pass in the Dangrek Mountains at O Smach connects northwestern Cambodia with Thailand. Despite this road and those running through a few other passes, in general the escarpment impedes easy communication between the two countries.
Between the western part of the Dangrek and the northern part of the Cardamom ranges, however, lies an extension of the Tonle Sap Basin that merges into lowlands in Thailand, which allows easy access from the border to Bangkok.
The Mekong Valley, which offers a communication route between Cambodia and Laos, separates the eastern end of the Dangrek Mountains and the northeastern highlands.
To the southeast, the basin joins the Mekong Delta, which, extending into Vietnam, provides both water and land communications between the two countries.