The history of Cambodia, a country in mainland Southeast Asia, can be traced back to at least the 5th millennium BC. Detailed records of a political structure on the territory of what is now Cambodia first appear in Chinese annals in reference to Funan, a polity that encompassed the southernmost part of the Indochinese peninsula during the 1st to 6th centuries. Centered at the lower Mekong, Funan is noted as the oldest regional Hindu culture, which suggests prolonged socio-economic interaction with maritime trading partners of the Indosphere in the west. By the 6th century a civilisation, called Chenla or Zhenla in Chinese annals, firmly replaced Funan, as it controlled larger, more undulating areas of Indochina and maintained more than a singular centre of power.