As a side trip of hong Kong Disneyland? Hong Kong is at the south most of China while Harbin is at the north most. You need to take flight to Harbin, or take direct train from Hong Kong to Beijing and then take train to Harbin, won't be cheap for a direct flight... You can check at Harbin Tours(https://www.travelchinaguide.com/package/harbin.htm) for more details about the travel fares.