Cambodia Historical Geography

Cambodia Historical Geography


Dr Steven A Martin

Cambodia is a small country with an awe-inspiring history, where natural resources and the opportunities presented by geography played a leading role in the development of one of the world’s greatest historical civilizations, the Khmer.

International students at Siem Reap, Cambodia | Khmer cultural tourism

Map showing the Tonle Sap in central Cambodia | Modified from: | Click to enlarge

Buddha faces at the Bayon | Angkor Thom, Cambodia

Water, Stone, Iron and Wood

The natural abundance of fresh water has always been the basis of agriculture and transport systems, thanks to the Mekong River (Mother of Waters) and the Tonle Sap (Great Lake), two of the world’s greatest hydrologic systems.

Meanwhile, ready access to stone, mainly rusty-red laterites and pastel sandstones, provided the building blocks of early civilization in the region.

Emboldened with hardwood forests, iron ore deposits, and the mastery of fire, the Khmer were empowered to build houses, fire kilns, and smelt ores and forge the tools and weapons of the largest ancient empire in mainland Southeast Asia.

The Mekong River

The Mekong is the 10th largest river in the world, and is the symbolic heart of tropical mainland Southeast Asia. Seasonal flooding brings silt and nourishment to the land, and nutrients and freshwater fish to the Tonle Sap, producing two ecologically vibrant outcomes, the floodplain and the flooded forest.

The floodplains receive water and minerals from as far away as Tibet, naturally irrigating and fertilizing enormous tracks of low-lying land, perfect for cultivation of rice and other food crops. As the Tonle Sap swells, it creates a flooded forest similar to the Amazon basin, where partially-submerged trees and their root systems create a haven for spawning fish.

Historically, fish resources on the Tonle Sap were among the most plentiful on Earth. Elderly fishermen still boast of the days of their youth when the Tonle Sap was so teeming with fish that all they had to do was row their open boats into the lake and wait for a full catch to jump in.

Mekong River | Click to view hi-res topography map of the Greater Mekong Subregion (GMS)

Mekong River at Sam Pun Boak | Ubon Ratchathani, Thailand | Click to Thai Geography Page

The Tonle Sap

The Tonle Sap is the largest freshwater lake in Asia and a global hot-spot of biodiversity, a valued sanctuary for migrating birds.

Tonle Sap River, which connects the lake with the Mekong, is the life-blood of the lake and one of the only rivers in the world to display an astonishing natural feature: the biannual flow reversal.

As rains brought by the Southwest Monsoon feed tributaries along the six countries of the Mekong (China, Myanmar, Thailand, Laos, Cambodia and Vietnam), the Tonle Sap River reverses the direction of its flow, and carries an extraordinary volume of water and fish species from the Mekong into the lake.

This remarkable hydrologic event occurs from June to October, when the river fills the lake to as much as five times its normal depth and area. In the dry season (November to April), water drains out of the lake and toward the Mekong.

The lake is the key source of food for nearly fifty-percent of the Cambodian people and represents the greatest inland fishery network in Asia. The Mekong and the Tonle Sap remain the life-blood of a country and its resilient people who use their local culture and knowledge to follow the seasonal changes of the monsoon to survive.

Tourism boats on the Tonle Sap, Southeast Asia's largest freshwater lake


Laterite, a soil type and stone comprised of compressed soil, is a product of the tropical Cambodian basin, where thousands of years of alternating wet and dry seasons and oscillating floods create the conditions for its formation. As a process, silicates are washed out of the soil, leaving iron and aluminum oxides to build up and form laterite.

Khmer architects learned many centuries ago how to cut cubes of this metallic mud-like rock from the ground in large blocks and set them to dry quickly, forming a near lava-like stone perfectly suited to building megalithic structures such as Angkor Wat.

Laterite is to Cambodia what limestone was to Egypt, a workable stone employed in the building of enormous structures that exemplify the historical geography of a great civilization.

However, compared with Egyptian limestone, laterite forms coarse blocks pitted with holes. It is difficult to prepare a clean, smooth surface with the aesthetic qualities desired for a religious monument.

"Laterite is to Cambodia what limestone was to the Egypt"

Tropical weathering, or "laterization" near the Tonle Sap

Laterite blocks drying in the sun at Siem Reap


On the other hand, sandstone, another resource available to the Khmers, is an exceptional facing stone. Sandstone was also used as a base for carving fine artwork such as bas-reliefs, many of which are still visible today in temples and monuments throughout Cambodia.

Phnom Kulen

A geographic blessing to the Khmer economy and collective conscious is Phnom Kulen, a forty kilometer long isolated chain of small sandstone mountain plateaus fifty kilometers to the northeast of Siem Reap.

Ancient sandstone quarry at Phnom Kulen

The Kulen Mountains are sacred to the Khmer and were the definitive source of sandstone throughout the Angkorian period (early 9th to 15th century).

River of 1000 Lingas | Kbal Spean | Phnom Kulen

Sandstone is a clean and sometimes colorfully pink soft stone, ideal for depicting the Apsara dancers (Khmer celestial nymphs) and many other Hindu and Buddha images still visible today.

The Kulen Mountains were a definitive stronghold against invading forces from Java during the early Khmer period, later forming a vital part of the Khmer empire’s political and cultural geography, and are still regarded by Cambodians today as the source of holy waters.

Apsara dancers in pink sandstone

Phnom Kulen | Sacred mountain and holy water of the Khmer

Iron and Fire

The early Cambodians developed a mastery of fire and built kilns to smelt ores, cast iron, and fire ceramics for pots and bowls used in households and temples for storing foods, water, and oils. Iron ore was an important natural resource in Khmer history, and ore deposits began to be exploited during the pre-Angkor period.

Khmer sword - Bronze handle - Iron blade - Dr Steven A Martin research

Khmer sword with bronze handle and iron blade

The Khmer demonstrated an early understanding of technologies needed for casting iron, particularly for tools and weapons. The need for iron ores and production drove development and distribution networks, including roads throughout the basin. Iron gave the Khmer purpose, unity, and regional superiority.

The Battle of Tonle Sap bas relief depicting warfare among the Khmer and Champa kingdoms

In this Day and Age

Angkor, formerly a city of nearly a million people, is the result of a complex interaction of cultural and industrial influences, whose natural resources provided the setting for a globally unique historical geography which gave birth to a civilization that, at its zenith, was arguably the greatest in the pre-industrialized world.

Young monks at Bantaey Srei historical site, Cambodia

Today, there is a renaissance of Khmer architectural and engineering spirit, unmistakably visible in the construction of new buildings and hotels in Siem Reap, Phnom Penh, and around the country.

After the horrors of the Pol Pot period, Cambodia has recovered as swiftly as jungle growing back over a ruined temple, and now the country is back on track as a vibrant economy which is one of the major engines of development at the heart of the ASEAN region.

Angkor Wat, Cambodia, receives millions of tourist per year

Perhaps more than ever, the sustainability of Cambodia’s unique natural resources and the natural gifts of her geography will once again play leading roles as a new Khmer civilization once more steps forward to take its rightful place among the world’s oldest and proudest human cultures.

Apsara Dancer | Classical Khmer performance art | Siem Reap, Cambodia

Personal Videos On Location

Short video clips featuring Cambodian national guide Ratha Singh. Mr Ratha shares his knowledge of Khmer history during our 2015 visit to Phnom Kulen, Siem Reap.

Phnom Kulen | Beng Mealea Temple

Phnom Kulen | River of 1000 Lingas

Siem Reap | Bas Relief at Angkor

Select Documentaries

There are currently a significant number of documentary films on Angkor Wat and the Khmer Empire of varying content and quality. Of these, I have selected three videos below for teaching the cultural and historical geographies of Cambodia and the Khmer Civilization.

Khmer Mystery | Fou-nan Lost City | With Charles Higham and Miriam Stark 41:00

Angkor Wat | Land of Gods (I)

Angkor Wat | Land of Gods (II)

Environmental Documentaries Mekong River and Tonle Sap

The building of dams throughout the Greater Mekong Subregion (GMS) affect the lives of millions of people and the ecology and biodiversity of the region.

Asian Development Bank | Saving Cambodia's Great Lake 22:39

About the Research

This research was inspired through experiences at the 2014 Indo-Pacific Prehistory Association (IPPA) in Siem Reap, and my 2015 tours to historical sites in Cambodia.

Siem Reap, Cambodia | David Blundell (left) | Steven Martin (center) | Charles Higham (right)

Special thanks to Prof. David BlundellProf. Charles HighamPeng Ponna (Mr. William) at Paññāsāstra University, and our Siem Reap guide, Ratha Seng.