The city of Vientiane once had three city walls - two perimeter walls made of brick, one encompassing the other, and between them a rectangular earthen rampart which predates the other two. Located in the area immediately west of the Phra That Luang monument, the rectangular earthen median wall had no brick core and was partially moated; fragments of it may still be seen today in the villages of Ban Nong Sang Tho, Ban Sibunheuang and Ban Thong Sang Nang in Muang Chanthaburi. This earthen rampart is thought to have been the earliest city wall in Vientiane, and given the religious significance of the nearby Phra That Luang site well before the establishment of the Lane Xang kingdom, it is not inconceivable that it once enclosed the capital of the ancient Mon kingdom of Candapuri. From at least the 11th century close links existed between this kingdom and the nearby region of Sayfong (modern Hadsayfong District of Vientiane Prefecture), where more than 30 vestiges, most believed to be of Mon origin, have be found within the vicinity of the modern villages of Sayfong Neua and Ban Sayfong Tai, including temple foundations, stupas, water tanks, wells and an extensive canal system. At some point between the 11th and 13th centuries both Candapuri/Chanthaburi and Sayfong fell under Tai control and Chanthaburi/Vientiane emerged as one of two capitals of Vientiane-Viengkham, setting the stage for the conquest of the region by King Fa Ngum and its integration into the Lane Xang mandala.