A form of monument which occurred only in Cambodia from the 9th-13th centuries AD. They are a series of artificial mountains on the Cambodian plain at Angkor, each crowned by shrines containing images of gods and of Khmer kings, their family, and their ancestors. The huge platforms of earth on which these buildings were founded are oriented east to west, the main gates facing east. Each king tried to outdo his predecessor in the height, size, and splendor of his temple mountain. The earlier ones are relatively small, though beautiful, while the later ones, such as Angkor Wat and the Bayon, are of stupendous size. It originated from the belief that the main temple of the king, which is the ritual center of the kingdom and eventually becomes his mausoleum, must be situated on a mountain or at least a hill. The architecture of the shrines themselves is relatively simple; it is based upon patterns invented in India, though the ornament of the shrines is often highly developed and characteristically Cambodian. On some of the temple mountains there are also relief panels illustrating various aspects of the royal mythology. The earliest surviving temple mountain at Angkor itself is the Bakong, probably finished in 881.