The period prior to the founding of the Qin Dynasty was a feudalistic era torn by 7 rival kingdoms. This period was also referred to as the Warring States period. Finally, in 221 BC, Shi Huang Di, from the kingdom of Qin succeeded in conquering all the other kingdoms, thus unifying all of ancient China. He proclaimed himself the First Emporer of the Qin Dynasty. During his rule, he abolished the various monetary systems, got rid of odd and curious shaped coins which were in the form of knife, spade, fish and others. He introduced the casting of the Qin Ban Liang cash coin, a round shaped coin with a central square hole weighting half a tael or 12 zhu. Qin coin denomination corresponds with its weight. Besides the introduction of China's first round coin, Shi Huang Di brought about the standardization and unification of laws, weights, measures, scripts and the guage (width between wheels) of wagons (or horse carts). However, despite these accomplishments, he was best remembered as the cruel Emperor who conscripted thousands of ordinary people to build the Great Wall of China. The building of this wall caused untold hardships and sufferings for the masses of conscripted labour.