
The Angkor regoin bordering the Great Lake with its valuable supply of water, fish, and fertile soil, has been settled since neolithic time, as is known from stone tools and ceremics found there, and from the identification of circular habitation sites from aerial photographs. For the whole Khmer country, there is more descriptive evidences from the account of Chinese, who began to trade and explore the commercial opportunities of mainland Southeast Asia in the early centuries of the Christian Era. The picture is one of small town-states, moated, fortified and frequently in conflict with each other. The Chinese called the principle country with which they traded Funan; it had a strategic importance in controlling the sea routes around the Mekong delta and the gulf of Thailand. In particular it controlled the narrow Isthmus of Kra - the neck of the Malay Peninsula - which connected eastern Asia with India. Indeed, it was trade with India that gave the Khmer their primary cultural contacts, and introduced them to Buddhism and Hinduism. Khmer religous beliefs, iconography, art and architecture all stemmed directly from India, and this had a profound influence on the development of its civilisation.
The 6th century sees the first historical evidence from local inscriptions. At around this time, the Chinese accounts begin to write of a kingdom called "Chenla" in the interior, but this is a Chinese rather than a Khmer name. In the second half of the century there is a record of a city called Bhavapura, with its king, Bhavavarman I extending his rule from near the present-day site of Kompong Thom to at least as far as Battambong in the west. He was succeeded by his brother, who ruled as Mahendravarman, who in turn was succeeded by his son, Isanavarman I. These three kings progressively conquered of the Khmer part of Funan, while the western part was taken by other people, in particular the Mons of the kingdom of Dvaravati to the W of Bangkok. Isanvavarman I was responsible for the temple at Sombor Prei Kuk, establishing the first of the Pre-Angkorean styles of architecture. Under Isanavarman's son, Bhavavarman II, who took the throne in 628, the empire disintegrated back into small states, and it took until 654 for Jayavarman I, a grandson of Isanavarman I, from of these princedoms, to reconquer much of the territory. There is evidence that he ruled from Aninditapura, close to Angkor. On his death, the empire again collapsed, and his successors, including his daughter Jayadevi, the only ancient Khmer queen, controlled only the small kingdom of Aninditapura. The country remained this way until the end of the eighth century, when Jayavarman II became king in 790.
Jayavarman II's conquest, first of Vyaadhapura (SE of Cambodia), then Sambhupura (Present-day Sambor), then N as far as Wat Phu, and finally of Aninditapura, established his power. He settled first at Hariharalaya, an ancient capital in the region of what is now Rolous, but then trying to go further NW, experienced an unknown setback which resulted in him relocated to the Kulen Plateau, some 30 km NE of Angkor. Here he pronounced himself "world emperor" in 802, but it was many years before he was strong enough to move his capital back to Hariharalaya on the shores of the Great Lake, where he died in 835.