What were things that Emperor Qin Shi Huang did that were significant?

He unified China, setting the stage for many dynasties in the future. He had the great wall built to ward off enemies to the north. He had the Terracotta army made, i am not entirely sure why, but i think to protect his tomb.

He made the terracotta army to show how dignified he was, also he didn't necessarily need it but because the ancient Chinese believed so strongly in myths and spirits they feared if they didn't please their dead ancestors that they would come back to haunt them in not just a way of giving people the spooks but they could demand for another burial, put someone in a flooded coffin and make someone else rescue them or even take someone from the living to the dead, and because Emperor Qin Shi Huang was so reckless, they didn't want his ghost to come back and do something so to keep him happy, they made what-ever he wanted for his tomb

He increased the entire trade route throughout China. With the unification of the Chinese currency he influenced the creation of the euro.