Most train routes in China aren't too scenic, but the line between Zhangye and Xining is well worth taking.
If you're going to Zhangye for the Danxia formations, bear in mind that all those photos you see of a dramatic red landscape have been heavily Photoshopped. I was disappointed.
Are you sure ZJJ has recovered enough from the earthquake to be worth visiting? It's a long trip there, worthwhile only if the park is in top shape.
Kaifeng lost all its charm around 20 years ago.
Zhengzhou never had any.
Fair points, 889. (Where would you recommend checking for ZJJ updates...besides here? Or, did you mean Jiuzhaigou?)
Zhengzhou would be for the wacky buildings and general mainland urban chaos, and Kaifeng for its history. On that note, have you been to Kashgar?
Now, it's looking more like substituting Zhangye for Erlian, with an eventual slog to Ulaanbaator.