Luang Prabang was important as the religious and royal capital of Lan Xang, but Vientiane was the largest most populous city (as well as the political capital beginning in 1560) and thus was of crucial commercial importance. Vientiane was originally a Mon city named "Chandapuri" or "City of the Moon." The Lao would change the name to "Vieng Chanthaburi Sisattanak" which means "Walled City of Sandalwood and a Million Nagas," later shortening it further to simply "Vieng Chan" (Vientiane). Sikhottabong in Khammouan and Nakon Phanom were also regional trading powers for central Lan Xang, just as Roi Et was crucial for overland trade on the Khorat Plateau.