Hi, I am travelling from Nanjing. How far is it and what trains would I take to Zhangjiajie?

Well, it is about 1,092km from Nanjing to ZJJ. No direct train can take you for the journey. Therefore, if you also wish to take trains, you need transfer to another train at Jingmen or Xiangyang of Hubei province. Thw whole journey takes a little longer tahn 24h.