Yes, it is very old since the ealiest great wall was much older than that we can see today. The Great Wall we see now was built in Ming Dynasty. The earliest wall was built by Chu Kingdom in Warning State period, 7th century BC. It was not the Great Wall we mean today. Qin connected the seperated walls together. The Great Wall came into being. It do help to win battles but there are still invaders break it. That's why the Qing Dynasty established and replaced Ming Dynasty.