The Phung Nguyen culture (modern northern Vietnam) and the Ban Chiang site (modern Thailand) account for the earliest use of copper by around 2,000 BCE, followed by the Dong Son culture, which by around 500 BCE had developed a highly sophisticated industry of bronze production and processing. Around the same time, the first "Agrarian Kingdoms" emerged whereby territory was abundant and favourable, such as Funan at the lower Mekong and Van Lang in the Red River delta. Smaller and insular principalities increasingly engaged in and contributed to the rapidly expanding sea trade.