Chengdu and Chongqing are both major hubs in China's national rail network. The two cities are connected by a bullet train that takes about two hours. It’s usually possible to buy tickets at the station on the day you want to travel if you don’t mind a bit of pushing and long lines. Reserve at least two weeks in advance if you plan to travel during major Chinese holidays. It is highly recommended to avoid travel during the Chinese New Year, usually celebrated each year around late January/early February, as the spectacular crush of people make all forms of travel (planes, trains, and especially buses) difficult and unpleasant.