Final answer:
The Khmer Empire was a Hindu-Buddhist empire that existed from the 9th to the 15th centuries in modern-day Cambodia, with Angkor Wat as its center. It saw a period of decline due to external invasions and environmental issues, and was eventually overtaken by a Thai kingdom.
Step-by-step explanation:
The Khmer Empire was a powerful mandala that lasted roughly from the 9th to the 15th centuries in what is now Cambodia. Its zenith was marked by the construction of Angkor Wat, an enormous complex of more than 900 temples, serving as the political and religious center of the empire. Kings of the Khmer Empire were considered incarnations of the Hindu god Vishnu. During the 13th century, the Bayon
Temple was built in the center of Angkor Thom, symbolizing Mt. Meru, the Buddhist cosmic mountain. The vast empire, which controlled much of Southeast Asia, was administratively sophisticated and divided into approximately 23 provinces.
Unfortunately, the decline of the Khmer Empire began due to revolts by areas such as Thailand, invasions by the Mongols, and environmental issues related to their water system. By 1431, a Thai kingdom conquered Angkor, bringing an end to the Khmer Empire.