Angkor is a name conventionally applied to the region of Cambodia serving as the seat of the Khmer empire that flourished from approximately the 9th century to the 15th century A.D. (The word "Angkor" itself is derived from the Sanskrit "nagara," meaning "city.") More precisely, the Angkorian period may be defined as the period from 802 A.D., when the Khmer Hindu monarch Jayavarman II declared himself the "universal monarch" and "god-king" of Cambodia, until 1431 A.D., when Thai invaders sacked the Khmer capital, causing its population to migrate south to the area of Phnom Penh.
The ruins of Angkor are located amid forests and farmland to the north of the Great Lake (Tonle Sap) and south of the Kulen Hills, near modern day Siem Reap (13°24'N, 103°51'E), and are a UNESCO World Heritage Site. The temples of the Angkor area number over one thousand, ranging in scale from nondescript piles of brick rubble scattered through rice fields to the magnificent Angkor Wat, said to be the world's largest single religious monument. Many of the temples at Angkor have been restored, and together they comprise the most significant site of Khmer architecture. Visitor numbers approach one million annually.

Historical Overview
The Angkorian period may be said to have begun shortly after 800 A.D., when the Khmer King Jayavarman II announced the independence of Kambujadesa (Cambodia) from Java and established his capital of Hariharalaya (now known as "Roluos") at the northern end of Tonle Sap. Through a program of military campaigns, alliances, marriages and land grants, he achieved a unification of the country bordered by China (to the north), Champa (to the east), the ocean (to the south) and a place identified by a stone inscription as "the land of cardamoms and mangoes" (to the west). In 802 Jayavarman articulated his new status by declaring himself "universal monarch" (chakravartin), and, in a move that was to be imitated by his successors and that linked him to the cult of Siva, taking on the epithet of "god-king" (devaraja)
Over the next 300 years, between 900 and 1200 AD, the Khmer empire produced some of the world's most magnificent architectural masterpieces in the area known as Angkor. Most are concentrated in an area approximately 15 miles east to west and 5 miles north to south, although the Angkor Archaeological Park which administers the area includes sites as far away as Kbal Spean, about 30 miles to the north. Some 72 major temples or other buildings dot the area.

Origin of Angkor as the Seat of the Khmer Empire
The principal temple of the Angkorian region, Angkor Wat, was built between 1113 and 1150 by King Suryavarman II. Suryavarman ascended to the throne after prevailing in a battle with a rival prince. An inscription says that in the course of combat, Suryavarman lept onto his rival's war elephant and killed him, just as the mythical bird-man Garuda slays a serpent. Suryavarman had the walls of the temple decorated with bas reliefs depicting not only scenes from mythology, but also from the life of his own imperial court. In one of the scenes, the king himself is portrayed as larger in size than his subjects, sitting cross legged on an elevated throne and holding court, while a bevy of attendants make him comfortable with the aid of parasols and fans.

Suryvarman II and the Construction of Angkor Wat
Following the death of Suryvarman around 1150 A.D., the kingdom fell into a period of internal strife. Its neighbors to the east, the Cham of what is now southern Vietnam, took advantage of the situation in 1177 to launch a seaborne invasion up the Mekong River and across Tonle Sap. The Cham forces were successful in sacking the Khmer capital of Yasodharapura and in killing the reigning king. However, a Khmer prince who was to become King Jayavarman VII rallied his people and defeated the Cham in battles on the lake and on the land. In 1181, Jayavarman assumed the throne. He was to be the greatest of the Angkorian kings.

Jayavarman VII, the Greatest of the Angkorian Kings
The year 1296 marked the arrival at Angkor of the Chinese diplomat Zhou Daguan. Zhou's one-year sojourn in the Khmer capital during the reign of King Indravarman III is historically significant, because he penned a still surviving account of approximately 40 pages detailing his observations of Khmer society. Some of the topics he addressed in the account were those of religion, justice, kingship, agriculture, slavery, birds, vegetables, bathing, clothing, tools, draft animals, and commerce. In one passage, he described a royal procession consisting of soldiers, numerous servant women and concubines, ministers and princes, and finally "the sovereign, standing on an elephant, holding his sacred sword in his hand." Together with the inscriptions that have been found on Angkorian stelas, temples and other monuments, and together with the bas-reliefs at the Bayon and Angkor Wat, Zhou's journal is our most significant source of information about everyday life at Angkor. Filled as it is with vivid anecdotes and sometimes incredulous observations of a civilization that struck Zhou as colorful and exotic, it is an entertaining travel memoire as well.

End of the Angkorian Period
It is widely believed that the abandonment of Angkor occurred as a result of the Thai invasions. Ongoing wars with the Thai were already sapping the strength of Angkor at the time of Zhou Daguan toward the end of the 13th century. In his memoirs, Zhou reported that the country had been completely devastated by such a war, in which the entire population had been obligated to participate. After the sack of Angkor in 1431, many persons, texts and institutions migrated to the Thai metropolis of Ayutthaya in the west, while others departed for the new center of Cambodian society at Phnom Penh in the south.

War with the Thai
Some scholars have connected the decline of Angkor with the conversion of Cambodia to Theravada Buddhism following the reign of Jayavarman VII, arguing that this religious transition eroded the Hindu conception of kingship that undergirded the Angkorian civilization.

Erosion of the state religion
According to George Coedès, the weakening of Angkor's royal government by ongoing war and the erosion of the cult of the devaraja undermined the government's ability to engage in important public works, such as the construction and maintenance of the waterways essential for irrigation of the rice fields upon which Angkor's large population depended for its sustenance. As a result, Angkorian civilization suffered from a reduced economic base, and the population was forced to scatter.

Neglect of public works
Other scholars attempting to account for the rapid decline and abandonment of Angkor have hypothesized natural disasters such as earthquakes, inundations, or drastic climate changes as the relevant agents of destruction.

Natural disaster
The great city and temples remained largely cloaked by the forest until the late 19th century when French archaeologists began a long restoration process. From 1907 to 1970 restoration of Angkor was under the direction of the École française d'Extrême-Orient, which worked to clear away the forest, repair foundations, and install drains to protect the buildings from water damage. In addition, scholars associated with the school initiated a program of historical scholarship and interpretation that is fundamental to the current understanding of Angkor. George Coedès, Maurice Glaize, Paul Mus, Philippe Stern and others made important contributions.
After the end of the Cambodia civil war, work began again, and since 1993 it has been jointly co-ordinated by the French, Japanese and UNESCO through the International Co-ordinating Committee on the Safeguarding and Development of the Historic Site of Angkor (ICC), while Cambodian work is carried out by the Authority for the Protection and Management of Angkor and the Region of Siem Reap (APSARA), created in 1995. Some temples have been carefully taken apart stone by stone and reassembled on concrete foundations. Since the end of the civil war, international tourism to Angkor has increased, posing additional conservation problems but also financial assistance to the restoration projects. Visitor numbers reached 900,000 in 2006.

Restoration and Preservation of Angkor
Historical Angkor was more than a site for religious art and architecture. It was the site of vast cities that responded to all the needs of a people, not only to specifically religious needs. Aside from a few old bridges, however, all of the remaining monuments are religious edifices. In Angkorian times, all non-religious buildings, including the residence of the king himself, were constructed of perishable materials, such as wood, "because only the gods had a right to residences made of stone." As a result, it is easier to write the history of Angkorian state religion than it is to write that of just about any other aspect of Angkorian society.
Several religious movements contributed to the historical developement of religion at Angkor:

Indigenous religious cults, including those centered on worship of the ancestors and of the lingam;
A royal personality cult, identifying the king with the deity, characteristic not only of Angkor, but of other Indic civilizations in southeast Asia, such as Champa and Java.
Hinduism, especially Shaivism, the form of Hinduism focussed on the worship of Shiva and the lingam as the symbol of Shiva, but also Vaishnavism, the form of Hinduism focussed on the worship of Vishnu;
Buddhism, in both its Mahayana and Theravada varieties. Religious History of Angkor
The religion of pre-Angkorian Cambodia, known to the Chinese as Chenla (550-800 A.D.), included elements of both Hinduism and indigenous ancestor cults.

Pre-Angkorian religion in Chenla
The Khmer king Jayavarman II, whose assumption of power around 800 A.D. marks the beginning of the Angkorian period, established his capital at a place called Hariharalaya (today known as Roluos), at the northern end of the great lake, Tonle Sap.

Shiva and the Lingam in Angkorian state religion
In the early days of Angkor, the worship of Vishnu was secondary to that of Shiva. The relationship seems to have changed with the construction of Angkor Wat by King Suryavarman II as his personal mausoluem at the beginning of the 12th century A.D. The central religious image of Angkor Wat was an image of Vishnu, and an inscription identifies Suryavarman as "Paramavishnuloka," or "he who enters the heavenly world of Vishnu." Suryavarman proclaimed his identity with Vishnu, just as his predecessors had claimed consubstantiality with Shiva.

Vaishnavism in the dedication of Angkor Wat
In the last quarter of the 12th century, King Jayavarman VII departed radically from the tradition of his predecessors when he adopted Mahayana Buddhism as his personal faith. Jayavarman also made Buddhism the state religion of his kingdom when he constructed the Buddhist temple known as the Bayon at the heart of his new capital city of Angkor Thom. In the famous face towers of the Bayon, the king represented himself as the bodhisattva Avalokiteshvara moved by compassion for his subjects.

Mahayana Buddhism under Jayavarman VII
The Hindu restoration began around 1243 A.D., with the death of Jayavarman VII's successor Indravarman II. The next king Jayavarman VIII was a Shaivite iconoclast who specialized in destroying Buddhist images and in reestablishing the Hindu shrines that his illustrious predecessor had converted to Buddhism. During the restoration, the Bayon was made a temple to Shiva, and its image of the Buddha was cast to the bottom of a well. Everywhere, cultic statues of the Buddha were replaced by lingams.

The Hindu Restoration
When Zhou Daguan came to Angkor in A.D. 1296, he found what he took to be three separate religious groups. The dominant religion was that of Theravada Buddhism. Zhou observed that the monks had shaven heads and wore yellow robes.

Religious Pluralism in the era of Zhou Daguan
In the course of the 13th century, Theravada Buddhism coming from Siam (Thailand) made its appearance at Angkor. Gradually it became the dominant religion of Cambodia, displacing both Mahayana Buddhism and Shaivism. The practice of Theravada Buddhism at Angkor continues until this day.

The triumph of Theravada Buddhism
The area of Angkor has many significant archaeological sites, including the following: Angkor Thom, Angkor Wat, Baksei Chamkrong, Banteay Kdei, Banteay Samré, Banteay Srei, Baphuon, the Bayon, Chau Say Tevoda, East Baray, East Mebon, Kbal Spean, the Khleangs, Krol Ko, Lolei, Neak Pean, Phimeanakas, Phnom Bakheng, Phnom Krom, Prasat Ak Yum, Prasat Kravan, Preah Khan, Preah Ko, Preah Palilay, Preah Pithu, Pre Rup, Spean Thma, Srah Srang, Ta Nei, Ta Prohm, Ta Som, Ta Keo, Terrace of the Elephants, Terrace of the Leper King, Thommanon, West Baray, West Mebon.

Archaeological Sites

Angkor is a Khmer term meaning "city." It comes from the Sanskrit nagara.
Banteay is a Khmer term meaning "citadel" or "fortress," which is also applied to walled temples.
Baray means "reservoir."
Esvara or Isvara is a suffix referring to the god Siva.
Gopura is a Sanskrit term meaning "entrance pavilion" or "gateway."
Jaya is a prefix meaning "victory."
Phnom is a Khmer term meaning "hill."
Prasat is a Khmer term meaning "tower." It comes from the Sanskrit prasada.
Preah is a Khmer term meaning "sacred" or "holy." (Preah Khan means "sacred sword.")
Srei is a Khmer term meaning "woman." (Banteay Srei means "citadel of women.")
Ta is a Khmer term meaning "ancestor" or "grandfather." (Ta Prohm means "Ancestor Brahma." Neak ta means "ancestors" or "ancestral spirits.")
Thom is a Khmer term meaning "big." (Angkor Thom means "big city.")
Varman is a suffix meaning "shield" or "protector." (Suryavarman means "protected by Surya, the sun-god.")
Wat is a Khmer term meaning (Buddhist) "temple." (Angkor Wat means "temple city.") See also
Books and Articles
News Reports

Audric, John (1972). Angkor and the Khmer Empire. London: R. Hale. ISBN 0-7091-2945-9. 
Chandler, David (1992). A History of Cambodia. Boulder: Westview Press. 
Coedès, George (1943). Pour mieux comprendre Angkor. Hanoi: Imprimerie d'Extrême Orient. 
Freeman, Michael; and Claude Jacques (1999). Ancient Angkor. Trumbull, Conn.: Weatherhill. ISBN 0-8348-0426-3. 
Higham, Charles (2001). The Civilization of Angkor. Berkeley: University of California Press. 
Stern, Philippe (1934). "Le temple-montagne khmèr, le culte du linga et le Devaraja," Bulletin de l'École française d'Extrême-Orient 34, pp. 611-616.
National Review: In Pol Pot Land: Ruins of varying types Sept 29, 2003.
UNESCO: International Programme for the Preservation of Angkor Accessed 17 May 2005.
"Climate change killed ancient city", The Australian, 2007-03-14. Retrieved on 2007-03-16. 
"Tourist invasion threatens to ruin glories of Angkor", The Observer, 2007-02-25.