Work started in 500 BC under [[Qin Shi Huang]], connecting older walls which were constructed by individual states. Most of the work was done in the [[Ming Dynasty]]. <ref>Susan Wise Bauer, ''The History of the Ancient World''</ref>Towers were built; originally as watchtowers, but later [[cannon]]s<ref>http://factsanddetails.com/china.php?itemid=27&catid=2&subcatid=1</ref> were added. | Work started in 500 BC under [[Qin Shi Huang]], connecting older walls which were constructed by individual states. Most of the work was done in the [[Ming Dynasty]]. <ref>Susan Wise Bauer, ''The History of the Ancient World''</ref>Towers were built; originally as watchtowers, but later [[cannon]]s<ref>http://factsanddetails.com/china.php?itemid=27&catid=2&subcatid=1</ref> were added. |