Begin your day in the morning with a visit to the magnificent Niushou Mountain (牛首山)which is the place to preserve the Buddha's parietal bone relic. You will find the splendid, amazing architectures. I will explain to you the history of the area with China's Buddhist culture. Spend 3-4 hours exploring the mountain and its surroundings.
After lunch, head to the Memorial Hall for the Victims in the Nanjing Massacre by Japanese Invaders. Spend 2 hours learning about the tragic events that took place during the 6-week massacre in 1937 (starting of World war 2). See numerous pieces of evidence and gain a deeper understanding of this dark chapter in history, it may beyond your understanding of human nature. Please be mentally prepared!
If you have other suggestions, let me know at any time, I will be happy to customise your travel plan.