One cultural common denominator of Southeast Asia has been the casting of elaborate bronze drums. The tradition began in the Dong Son period (ca. 1000 BC) when wet rice cultivation, the cult of ancestor worship, animal domestication and bronze casting spread throughout Southeast Asia. The drums represented wealth and prestige. Fertility symbols, such as frogs, were frequent motifs as well as elaborate geometric designs. These ancient drums are from the Red River Valley of present day northern Vietnam and date to approximately 300 BC.