Check this before you book a flight. Ordinary-passport holders from 50 countries can enter visa-free for up to 30 days for tourism, business, family visits or transit: Andorra, Austria, Belgium, Bulgaria, Croatia, Cyprus, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Luxembourg, Malta, Monaco, Montenegro, the Netherlands, North Macedonia, Norway, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Switzerland, the United Kingdom, Australia, New Zealand, Argentina, Brazil, Canada, Chile, Peru, Uruguay, Bahrain, Brunei, Japan, Kuwait, Oman, South Korea and Saudi Arabia. For most of these countries the exemption runs to 31 December 2026, so check the NIA list if you travel later. The United States is not on it.
Citizens of 57 countries, the United States among them, can instead use the 240-hour (10-day) visa-free transit, with an ordinary passport and a confirmed onward ticket to a third country or region (not China, and not the place you flew in from). You enter through any of the 65 designated ports and can make cross-province visits in the permitted areas of the 24 provinces involved, so the NIA rules cover entering at Chongqing Jiangbei Airport, a designated port with a dedicated area for transit applications, and taking the train to Chengdu in Sichuan. Dazu and Wulong are inside Chongqing. Other nationalities need a visa or a bilateral exemption; start at the NIA site. Fill in the free online arrival card on the official NIA page before you land. Paid copies exist and aren't needed.