ong wan ch eng , ▁which ▁means ▁the ▁" city ▁r uling ▁ten ▁thousand ", ▁is ▁the ▁largest ▁urban ▁center ▁of ▁the ▁Southern ▁X ion gnu ▁that ▁has ▁ever ▁been ▁found . ▁ ▁The ▁city ' s ▁ru ins ▁are ▁well ▁preserved ▁and ▁located ▁in ▁J ing bian ▁County , ▁Sh a an xi ▁Province , ▁near ▁the ▁border ▁with ▁Inner ▁Mong olia . ▁ ▁The ▁city ▁has ▁been ▁survey ed ▁and ▁has ▁had ▁some ▁elements ▁restored , ▁but ▁not ▁yet ▁fully ▁exc av ated . ▁ ▁The ▁city ▁was ▁built ▁by ▁around ▁ 1 0 0 , 0 0 0 ▁X ion gnu ▁of ▁the ▁X ia ▁kingdom ▁under ▁the ▁command ▁of ▁Hel ian ▁Bob o ▁in ▁ 4 1 9 . ▁ ▁Hel ian ▁Bob o , ▁also ▁known ▁by ▁his ▁sin ified ▁surname ▁as ▁Li u ▁Bob o , ▁was ▁a ▁desc endant ▁of ▁the ▁X ion gnu ▁ch any u ▁(" king ") ▁who ▁founded ▁their ▁ste ppe ▁emp ire ▁in ▁the ▁ 3 rd ▁century ▁BC . ▁ ▁Hel ian ▁Bob o ▁died ▁in ▁ 4 2 5 ▁AD , ▁and ▁Hel ian ▁Ch ang ▁succeeded ▁him ▁as ▁r uler ▁of ▁the ▁city . ▁ ▁The ▁Great ▁Wall ▁of ▁China ▁was ▁built ▁to ▁contain ▁the ▁X ion gnu ▁threat , ▁and ▁T ong wan ch eng ▁was ▁the ▁main ▁X ion gnu ▁capital ▁that ▁stood ▁on ▁other ▁side ▁of ▁that ▁wall . ▁The ▁city ▁was ▁largely ▁of ▁wood ▁construction ▁and ▁had ▁very ▁thick ▁outer ▁walls ▁which ▁were ▁colored