Nanjing, beautifully situated in the Yangtze River Delta, is home to more than 8 million people. It lies approximately 300 kilometres to the west of Shanghai and is one of the transportation hubs in eastern China. The city is divided by the Yangtze, the city centre being on the south bank but several other districts lying north of the river. It's a renowned historical and cultural city with multiple historical sites which played an important part in Chinese history having served as the capital of several dynasties, kingdoms and republican governments. It's part of the "Four Great Ancient Capitals of China", the other three being Beijing, Luoyang and Xi'an.
Start your day at the Skyways Bakery (1, 160 Shanghai Rd, Gulou) to get a proper breakfast. Especially if you're already travelling a long time in China you'll value a proper bread roll and some good coffee. They do have other imported goods and you're able to create your own sandwich. After that make your way to the close by Zifeng Tower (2, 1 Zhongyang Rd, Gulou). This 450-metre high supertall skyscraper boosts some great views over the city, but be aware that the view can be quite restricted because of smog. The tower was completed in 2010 and designed by Skidmore, Owings & Merrill LLP.
From here head to the City Wall of Nanjing. The Xuanwumen gate (3, 1 Xuanwumen Rd, Gulou) is in walking distance from the Zifeng Tower, from there you can head north towards the Shencemen Yuecheng Park (4, 8 Longpan Rd, Xuanwu), the Xuanwu Lake always on your right side. Soak up the wonderful atmosphere, calm lake view on the right side, busy city view on the left side. Now it's time for a change of scenery, take the Metro to the Nanjing Yangtze River Bridge which is located in the north-west of the city (5). The bridge was completed in 1968 and was the last link for the Beijing-Shanghai Railway. It's a pretty impressive structure including communist air, you can visit the south of the bridge, just enter the park below the bridge, pay the small entrance fee and head to the pillar which is closest to the water to find an elevator to the top. The next trip is quite far so you better take a taxi this time. The Nanjing Massacre Memorial Hall is located in the south of Nanjing (6, 418 Shuiximen St, Jianye) and pays tribute to the 40,000 to over 300,000 victims during the Nanjing Massacre in 1937 & 1938. A gruesome and depressing reminder of the cities place in the Second Sino-Japanese War and World War II. From here the Gate of China is very close, it's the southernmost gate of the city wall (7). Last stop on the tour is the Confucius Temple (8, 128 Zinyhan Rd, Qinhuai), once a place to worship Confucius it's now part of a huge complex which also hosts the Jiangnan Examination Hall.
One day is very limited so you may want to switch certain parts of this trip, e.g. the ruins of the Ming Dynasty Imperial Palace or the Presidential Palace are worth a look too. Be sure to check out the travel guide on Wikivoyage and the website of the Nanjing Municipal Tourism Commission.