Nong Bua Lamphu was where the Lao defeated Ayutthaya in 1571, and was the site of a major battle against King Anouvong in 1827 when the city was totally destroyed by Thailand for its symbolic importance. Roi Et on the southern Khorat Plateau was also heavily fortified, and had been founded by the Khmer as a major trading center between the Pao, Mun and Chi Rivers. Trade cities also existed at Loei, and Nong Han Noi on the Song Khram River.