The Khmer Empire was one of the most powerful empires in Southeast Asia, based in what is now Cambodia and flourishing from the 9th to the 15th century. The empire, which grew out of former kingdom of Chenla, at times ruled over and/or vassalized parts of modern-day Laos, Thailand, Vietnam, Myanmar, and Malaysia.

The beginning of the era of the Khmer kingdom is conventionally dated to 802 AD. In this year, King Jayavarman II had himself declared him a Wheel-Turning Monarch (Chakravartin) and King of the Gods (Devaraja) on Mount Kulen, initiating the cult of the Divine Monarch which characterised the Empire.

Its greatest legacy is Angkor, the site of the capital city during the empire's zenith. Angkor bears testimony to the Khmer empire's immense power and wealth, as well as the variety of belief systems that it patronised over time. The empire's official religions included Hinduism and Mahayana Buddhism, until Theravada Buddhism prevailed, even among the lower classes, after its introduction from Sri Lanka in the 13th century.

Modern researches by satellites have revealed Angkor to be by far the largest pre-industrial urban center in the world, being around 1,000 sq km or roughly the size of Los Angeles. Its nearest rival in the ancient world was Tikal, a Mayan city in Guatemala, which covers between 100 and 150 sq km. It is estimated that well over a half a million people were living in the area, which was sustained through a large complex of reservoirs and irrigation schemes in which the temples played a large part.

The three greatest Kings were Jayavarman II (reigned 802 - 850 A.D.), who founded the empire; Suryavarman II (reigned 1113 - 1150 A.D.) who built what is now known as Angkor Wat; and Jayavarman VII (reigned 1181-1219 A.D.), a Mahayana Buddhist King who was one of the greatest builders in history.

Jayavarman VII (1125 - 1215) was a king of the Khmer Empire (c.1181-1215) in present day Siem Reap, Cambodia. He was the son of King Dharanindravarman II (r. 1150-1160) and Queen Sri Jayarajacudamani. He married Jayarajadevi and then, after her death, married her sister Indradevi. The two women are commonly thought to have been a great inspiration to him, particularly in his unusual devotion to Buddhism.

Jayavarman probably spent his early years away from the Khmer capital. He may have spent time among the Cham of modern-day Vietnam. The Cham shared with the Khmer the Hindu and Buddhist religions, as well as the use of Sanskrit as a formal language.

In 1177 and again in 1178, the Cham invaded Cambodia. In 1178, they launched a surprise attack on the Khmer capital by sailing a fleet up the Mekong River, across Lake Tonle Sap, and then up the Siem Reap River, a tributary of the Tonle Sap. The invaders pillaged the Khmer capital of Yasodharapura and put the king to death, as well as taking the Apsara dancers.

In the same year Jayavarman came into historical prominence by leading a Khmer army that ousted the invaders. At the time, he may already have been in his 60s. Returning to the capital, he found it in disorder. He put an end to the disputes between warring factions and in 1181 was crowned king himself. Early in his reign, he probably repelled another Cham attack, quelled a rebellion, and rebuilt the capital of Angkor.

Over the 30 some years of his reign, Jayavarman embarked on a grand program of construction that included both public works and monuments. As a Mahayana Buddhist, his declared aim was to alleviate the suffering of his people. One inscription tells us: "He suffered from the illnesses of his subjects more than from his own; the pain that affected men's bodies was for him a spiritual pain, and thus more piercing." This declaration must be read in light of the undeniable fact that the numerous monuments erected by Jayavarman must have required the labor of thousands of workers.

Historians have identified three stages in Jayavarman's building program. In the first stage, he focussed on useful constructions, such as hospitals, rest houses along the roads, and reservoirs. Thereafter, he built a pair of temples to venerate his parents: Ta Prohm was built in honor of his mother and Preah Khan in honor of his father. He also built the Buddhist University of Banteay Kdei, where Queen Indradevi was one of the main teachers in Buddhist Philosophy. Finally, he constructed his own "temple-mountain" at Bayon and developed the city of Angkor Thom around it.