The Ancient Tombs at Longtou Mountain (simplified Chinese: 龙头山古墓群; traditional Chinese: 龍頭山古墓群; pinyin: Lóngtóushān gǔmùqún, Hangul: 육정산 고분군) are the burial sites of twelve royal figures from the Balhae Kingdom. It is located southeast of Toudao Township on Longtou Mountain, (头道镇), Helong County (和龙市), Yanbian Korean Autonomous Prefecture, Jilin, China, a region possibly called "the Western Field of the Ran Valley"(染谷之西原) by the Balhae people. The famous Mausoleum of Princess Jeonghyo is located here. The tomb covers an area of 500 metres east to west, and 400 metres north to south. The tombs have been considered a unit of the third series of Protected National Cultural Artifacts (重点文物保护单位) since January 13, 1988. The walls and the murals of the tomb have been covered with anti-corrosive chemicals; at one point the tomb included at least one tower, but it is no longer standing.