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. Vientiane's inner perimeter wall is believed to have been constructed in the mid 16th century when King Sai Setthathirat I relocated the capital of Lane Xang from Luang Prabang to Vientiane, but very little evidence of it now remains; maps dating from the French colonial period and remnants unearthed in recent years during construction work suggest that the inner wall was approximately five kilometres in length and started at the confluence of the Pak Passak and Mekong Rivers just west of present-day Wat Chanthaburi (Wat Chan), following what is now Thanon Khun Burom north eastwards through Ban Sihom before returning south west along the same road to the Morning Market area. Thereafter it continued in a south-westerly direction along what is now Thanon Khouvieng before returning to the Mekong River embankment at Ban Khangone Tai. At a later stage it would appear to have been extended one kilometre further south to embrace Ban Sokpaluang and Ban Wat Nak, rejoining the Mekong embankment at Ban Thaphalanxay (Thanon Thadeua kilometre 4). The focus of the area enclosed by this inner wall was the royal palace, situated in the city centre area now bordered by Thanon Fa Ngum, Thanon Chanthakhoummane, Thanon Samsenthai and Thanon Mahasot, which includes the modern Presidential Palace, Wat Sisakhet, Ho Phra Keo, and the Ministry of Information and Culture and Ministry of Education buildings. Today the only substantial surviving sections of Vientiane's city walls are those of the outer perimeter wall, which was constructed for defensive purposes between 1770 and 1828 and is believed to have stretched at least 30 kilometres in length. While the westernmost part of this wall may also originally have started at the Mekong embankment, surviving sections only commence some two kilometres north of the city centre in Ban Hua Khusut (at the confluence of the Pak Passak and Hongseng Rivers), extending eastwards through Ban Hongseng (Muang Chanthaburi) and Ban Sawang (Muang Saysettha) and then heading south into Ban Dongkhoi, Ban Nonghai Tai and Ban Dongdoo (Muang Hadsayfong) before rejoining the Mekong midway between Ban Bo O and Ban Tha Na (Muang Hadsayfong). Principal sites where the outer perimeter wall may be seen are (i) earthworks located in the area west of the bridge in Ban Hongseng; (ii) earthworks located close to the entrance of the Lao-American College in Ban Sawang (the latter recently enclosed in a protective wall which was funded by the College); (iii) a 25-metre intact section of wall located in Ban Nonghai Tai; and (iv) earthworks located in Ban Donedoo. In 2000, with sponsorship from UNESCO, a Vientiane City Walls Research and Exhibition Centre was constructed next to the largest surviving (south eastern) section of wall in Ban Nonghai Tai, complete with a canopy to protect the adjacent wall from the weather: