The Mekong River formed the political and economic arteries for the Kingdom of Lan Xang, so much so that the Chinese name for the river "Lán Cāng" 瀾滄 is synonymous with the Lao kingdom. The river provided the means for the people, commerce and armies of Lan Xang to move between regional power centers, but also formed important geographic and defensive barriers. Major rapids formed the boundaries between the areas (and subsequent kingdoms) of Luang Prabang, Vientiane and Champasak. The Khone Falls and Si Phan Don region were not navigable and provided a natural defense for Lan Xang from invasion coming upriver.