The Tenth Doctor and Donna arrive in China during the Qin dynasty, "A couple of centuries BC". The Great Wall of China is still being built. Before the Doctor can stop her, Donna takes photos with her mobile phone. They are captured and thrown into a pit, where they battle a robot made of pottery. They defeat it using Donna's phone signal. The Doctor and Donna run away just before the whole palace blows up, burying the army. It will be found again centuries later and become one of the greatest discoveries of mankind.