Supporting cities were found along the Khorat Plateau, and were based on trade or military importance. Say Fong was a Khmer trading post which became famous as a Lao cultural center for writing and arts. Vieng Khuk was mentioned by Van Wuysthoff, and was the "port city" for Vientiane, where trade between Chinese merchants took place before being destroyed in the Lao-Siamese War in 1827. South of Vientiane on the Khorat Plateau, Nong Bua Lamphu (or Muang Dan) was a major fortified city and traditionally administered by the Lao crown princes.