Prehistoric artefacts are often found during mining activities in Ratanakiri. Iron was worked by about 500 BC, with supporting evidence coming from the Khorat Plateau, in modern-day Thailand. In Cambodia, some Iron Age settlements were found beneath Baksei Chamkrong and other Angkorian temples while circular earthworks at the site of Lovea a few kilometres north-west of Angkor. Burials, much richer than other types of finds, testify to improvement of food availability and trade (even on long distances: in the 4th century BC trade relations with India were already opened) and the existence of a social structure and labour organisation. Among the artifacts from the Iron Age, glass beads are important evidence. Different kinds of glass beads recovered from several sites across Cambodia, such as the Phum Snay site in the northwest and the Prohear site in the southeast, show that there were two main trading networks at the time. The two networks were separated by time and space, which indicate that there was a shift from one network to the other at about 2nd–4th century AD, probably with changes in socio-political powers. Pre-Angkorian and Angkorian era During the 3rd, 4th, and 5th centuries, the Indianised states of Funan and its successor, Chenla, coalesced in present-day Cambodia and southwestern Vietnam. For more than 2,000 years, what was to become Cambodia absorbed influences from India, passing them on to other Southeast Asian civilisations that are now Thailand and Laos. Little else is known for certain of these polities, however Chinese chronicles and tribute records do make mention of them. It is believed that the territory of Funan may have held the port known to Alexandrian geographer Claudius Ptolemy as "Kattigara". The Chinese chronicles suggest that after Jayavarman I of Chenla died around 681, turmoil ensued which resulted in the division of the kingdom into Land Chenla and Water Chenla which was loosely ruled by weak princes under the dominion of Java. The Khmer Empire grew out of these remnants of Chenla, becoming firmly established in 802 when Jayavarman II (reigned – ) declared independence from Java and proclaimed himself a Devaraja. He and his followers instituted the cult of the God-king and began a series of conquests that formed an empire which flourished in the area from the 9th to the 15th centuries. During the rule of Jayavarman VIII the Angkor empire was attacked by the Mongol army of Kublai Khan, however,