I do not know Nanning. If you like history, I would take the train to Xi'an. That is where the Terra Cotta Soldiers are. A 6000 year old village, the birthplace of Chinese Buddhism, Temples and so much more. Of course you could go to Beijing, there are a number of things there too. The Wall, tiannemon Square,
Summer Palace, Mao's Tomb, The palace of good harvests, The Zoo and many other things to do there also. Unless you wanted to just stay in Nanning, there are a lot of other places to go to. The train is cheap and so are in country flights. Just dont book them online, you will pay up to twice as much. I found that out. Most of the time, let her book you into the hotel. She will get it at a cheaper rate than you can.