The great Laotian epic, the Phra Lak Phra Lam, claims that Prince Thattaradtha founded the city when he left the legendary Lao kingdom of ''Muong Inthapatha Maha Nakhone'' because he was denied the throne in favor of his younger brother. Thattaradtha founded a city called ''Maha Thani Si Phan Phao'' on the western banks of the Mekong River; this city was said to have later become today's Udon Thani, Thailand. One day, a seven-headed Naga told Thattaradtha to start a new city on the east bank of the river opposite ''Maha Thani Si Phan Phao''. The prince called this city ''Chanthabuly Si Sattanakhanahud''; which was said to be the predecessor of modern Vientiane.